<s>
1991	O
saw	O
many	O
sequels	O
and	O
prequels	O
in	O
video	O
games	O
,	O
such	O
as	O
Street	B-Application
Fighter	I-Application
II	I-Application
,	O
Final	B-Application
Fantasy	I-Application
IV	I-Application
,	O
Super	B-Application
Castlevania	I-Application
IV	I-Application
,	O
Mega	B-Application
Man	I-Application
4	I-Application
,	O
Super	B-Application
Ghouls	I-Application
'	I-Application
n	I-Application
Ghosts	I-Application
,	O
and	O
The	B-Application
Legend	I-Application
of	I-Application
Zelda	I-Application
:	I-Application
A	I-Application
Link	I-Application
to	I-Application
the	I-Application
Past	I-Application
,	O
along	O
with	O
new	O
titles	O
such	O
as	O
Sonic	B-Application
the	I-Application
Hedgehog	I-Application
,	O
Battletoads	B-Application
,	O
Lemmings	B-Application
,	O
Sunset	B-Application
Riders	I-Application
,	O
Duke	B-Application
Nukem	I-Application
,	O
Fatal	B-Application
Fury	I-Application
:	I-Application
King	I-Application
of	I-Application
Fighters	I-Application
,	O
and	O
Streets	B-Application
of	I-Application
Rage	I-Application
.	O
</s>
<s>
The	O
year	O
's	O
highest-grossing	O
video	O
game	O
worldwide	O
was	O
Capcom	O
's	O
arcade	B-Application
fighting	O
game	O
Street	B-Application
Fighter	I-Application
II	I-Application
.	O
</s>
<s>
The	O
year	O
's	O
best-selling	O
home	O
system	O
was	O
the	O
Game	B-Device
Boy	I-Device
for	O
the	O
second	O
year	O
in	O
a	O
row	O
,	O
while	O
the	O
year	O
's	O
best-selling	O
home	O
video	O
game	O
was	O
Sega	O
's	O
Sonic	B-Application
the	I-Application
Hedgehog	I-Application
,	O
which	O
was	O
also	O
the	O
year	O
's	O
top	O
video	O
game	O
rental	O
in	O
the	O
United	O
States	O
.	O
</s>
<s>
The	O
year	O
's	O
highest-grossing	O
game	O
worldwide	O
was	O
Street	B-Application
Fighter	I-Application
II	I-Application
,	O
which	O
alone	O
accounted	O
for	O
an	O
estimated	O
60%	O
of	O
the	O
global	O
arcade	B-Application
game	O
market	O
,	O
according	O
to	O
Coinslot	O
magazine	O
.	O
</s>
<s>
The	O
following	O
table	O
lists	O
the	O
year	O
's	O
top-grossing	O
arcade	B-Application
game	O
in	O
Japan	O
,	O
the	O
United	O
Kingdom	O
,	O
United	O
States	O
,	O
and	O
worldwide	O
.	O
</s>
<s>
In	O
Japan	O
,	O
the	O
following	O
titles	O
were	O
the	O
top	O
ten	O
highest-grossing	O
arcade	B-Application
games	O
of	O
1991	O
,	O
according	O
to	O
the	O
annual	O
Gamest	O
and	O
Game	O
Machine	O
charts	O
.	O
</s>
<s>
In	O
the	O
United	O
States	O
,	O
the	O
following	O
titles	O
were	O
the	O
highest-grossing	O
arcade	B-Application
video	I-Application
games	I-Application
of	O
1991	O
.	O
</s>
<s>
In	O
Hong	O
Kong	O
and	O
Australia	O
,	O
the	O
following	O
titles	O
were	O
the	O
top-grossing	O
arcade	B-Application
games	O
on	O
the	O
monthly	O
charts	O
in	O
1991	O
.	O
</s>
<s>
Sonic	B-Application
the	I-Application
Hedgehog	I-Application
was	O
the	O
best-selling	O
home	O
video	O
game	O
of	O
1991	O
,	O
with	O
copies	O
sold	O
worldwide	O
during	O
the	O
year	O
.	O
</s>
<s>
In	O
the	O
United	O
Kingdom	O
,	O
the	O
following	O
titles	O
were	O
the	O
best-selling	O
home	O
video	O
games	O
on	O
the	O
monthly	O
Computer	B-Device
and	O
Video	O
Games	O
(	O
CVG	O
)	O
charts	O
in	O
1991	O
.	O
</s>
<s>
February	O
14	O
–	O
DMA	O
Design	O
releases	O
Lemmings	B-Application
,	O
a	O
puzzle	O
game	O
that	O
requires	O
the	O
player	O
to	O
lead	O
a	O
group	O
of	O
lemmings	B-Application
through	O
a	O
dangerous	O
environment	O
to	O
an	O
escape	O
portal	O
.	O
</s>
<s>
February	O
6	O
–	O
Capcom	O
releases	O
Street	B-Application
Fighter	I-Application
II	I-Application
for	O
arcades	O
.	O
</s>
<s>
It	O
is	O
also	O
credited	O
with	O
revitalizing	O
the	O
arcade	B-Application
game	O
industry	O
at	O
the	O
time	O
,	O
and	O
popularizing	O
direct	O
tournament-level	O
competition	O
between	O
players	O
.	O
</s>
<s>
March	O
–	O
AOL	O
,	O
SSI	O
,	O
TSR	O
and	O
Stormfront	O
Studios	O
collaborate	O
and	O
launch	O
Neverwinter	B-Application
Nights	I-Application
,	O
credited	O
as	O
the	O
first	O
graphical	O
MMORPG	B-Protocol
.	O
</s>
<s>
May	O
6	O
–	O
Sierra	O
On-Line	O
releases	O
The	O
Sierra	O
Network	O
,	O
which	O
is	O
also	O
credited	O
as	O
the	O
first	O
graphical	O
MMORPG	B-Protocol
(	O
due	O
to	O
its	O
inclusion	O
of	O
The	B-Protocol
Shadow	I-Protocol
of	I-Protocol
Yserbius	I-Protocol
)	O
,	O
TSN	O
would	O
later	O
become	O
its	O
more	O
memorable	O
name	O
,	O
ImagiNation	O
Network	O
,	O
after	O
a	O
total	O
buyout	O
from	O
AT&T	O
in	O
1994	O
.	O
</s>
<s>
June	O
23	O
–	O
Sega	O
releases	O
Sonic	B-Application
the	I-Application
Hedgehog	I-Application
for	O
the	O
Sega	B-Operating_System
Genesis	I-Operating_System
which	O
later	O
becomes	O
the	O
pack-in	O
game	O
and	O
defining	O
title	O
for	O
the	O
console	B-Device
.	O
</s>
<s>
It	O
introduces	O
the	O
eponymous	O
character	O
,	O
who	O
would	O
go	O
on	O
to	O
be	O
Sega	O
's	O
mascot	B-Application
.	O
</s>
<s>
July	O
19	O
–	O
Square	O
releases	O
Final	B-Application
Fantasy	I-Application
IV	I-Application
in	O
Japan	O
,	O
the	O
first	O
Final	B-Application
Fantasy	I-Application
game	I-Application
for	O
the	O
Super	B-Application
Famicom	I-Application
(	O
released	O
in	O
November	O
as	O
Final	B-Application
Fantasy	I-Application
II	I-Application
in	O
North	O
America	O
)	O
.	O
</s>
<s>
August	O
13	O
–	O
Intelligent	O
Systems	O
releases	O
SimCity	B-Application
for	O
the	O
Super	B-Application
Nintendo	I-Application
Entertainment	I-Application
System	I-Application
.	O
</s>
<s>
August	O
23	O
–	O
Nintendo	O
releases	O
Super	B-Application
Mario	I-Application
World	I-Application
and	O
F-Zero	B-Application
along	O
with	O
the	O
Super	B-Application
Nintendo	I-Application
Entertainment	I-Application
System	I-Application
in	O
North	O
America	O
.	O
</s>
<s>
Super	B-Application
Mario	I-Application
World	I-Application
was	O
the	O
original	O
pack-in	O
game	O
for	O
the	O
SNES	B-Application
.	O
</s>
<s>
The	O
game	O
introduces	O
the	O
Yoshi	B-Application
character	O
to	O
the	O
Mario	B-Application
series	I-Application
.	O
</s>
<s>
September	O
–	O
Namco	O
releases	O
Starblade	B-Application
for	O
arcades	O
,	O
featuring	O
one	O
of	O
the	O
earliest	O
instances	O
of	O
real-time	O
3D	O
graphics	O
in	O
video	O
games	O
.	O
</s>
<s>
September	O
–	O
Electronic	O
Arts	O
releases	O
motorcycle	O
racing	O
combat	O
game	O
Road	B-Device
Rash	I-Device
for	O
Sega	B-Operating_System
Genesis	I-Operating_System
,	O
starting	O
the	O
series	O
.	O
</s>
<s>
November	O
–	O
Nintendo	O
releases	O
Metroid	B-Application
II	I-Application
:	I-Application
Return	I-Application
of	I-Application
Samus	I-Application
for	O
the	O
Game	B-Device
Boy	I-Device
in	O
North	O
America	O
.	O
</s>
<s>
November	O
–	O
Delphine	O
Software	O
releases	O
cinematic	O
action-adventure	O
game	O
Another	B-Application
World	I-Application
for	O
the	O
Amiga	B-Device
,	O
which	O
uses	O
polygons	B-General_Concept
instead	O
of	O
sprites	O
.	O
</s>
<s>
November	O
21	O
–	O
Nintendo	O
releases	O
The	B-Application
Legend	I-Application
of	I-Application
Zelda	I-Application
:	I-Application
A	I-Application
Link	I-Application
to	I-Application
the	I-Application
Past	I-Application
for	O
the	O
Super	B-Application
Famicom	I-Application
in	O
Japan	O
.	O
</s>
<s>
November	O
25	O
–	O
SNK	O
releases	O
Fatal	B-Application
Fury	I-Application
:	I-Application
King	I-Application
of	I-Application
Fighters	I-Application
for	O
the	O
Neo	B-Application
Geo	I-Application
.	O
</s>
<s>
December	O
1	O
–	O
LucasArts	O
releases	O
Monkey	B-Application
Island	I-Application
2	I-Application
:	I-Application
LeChuck	I-Application
's	I-Application
Revenge	I-Application
for	O
Amiga	B-Device
,	O
MS-DOS	O
,	O
Macintosh	B-Device
,	O
and	O
FM	O
Towns	O
.	O
</s>
<s>
December	O
4	O
–	O
Konami	O
releases	O
Super	B-Application
Castlevania	I-Application
IV	I-Application
for	O
SNES	B-Application
in	O
North	O
America	O
.	O
</s>
<s>
December	O
6	O
–	O
Mega	B-Application
Man	I-Application
4	I-Application
is	O
released	O
in	O
Japan	O
.	O
</s>
<s>
December	O
13	O
–	O
Tecmo	O
releases	O
Tecmo	B-Application
Super	I-Application
Bowl	I-Application
for	O
NES	B-Language
,	O
the	O
follow-up	O
to	O
1989	O
's	O
Tecmo	B-Application
Bowl	I-Application
.	O
</s>
<s>
December	O
16	O
–	O
MicroProse	O
releases	O
Civilization	B-Application
.	O
</s>
<s>
Team17	O
release	O
Alien	B-Application
Breed	I-Application
,	O
the	O
first	O
of	O
the	O
series	O
,	O
for	O
the	O
Amiga	B-Device
.	O
</s>
<s>
July	O
–	O
Atari	O
updates	O
their	O
Lynx	O
handheld	B-Application
system	O
with	O
a	O
smaller	O
form-factor	O
,	O
better	O
screen	O
,	O
and	O
longer	O
battery	O
life	O
.	O
</s>
<s>
August	O
23	O
–	O
Super	B-Application
Nintendo	I-Application
Entertainment	I-Application
System	I-Application
released	O
in	O
North	O
America	O
.	O
</s>
<s>
December	O
1	O
–	O
Sega	O
releases	O
the	O
Mega-CD	B-Device
in	O
Japan	O
.	O
</s>
<s>
September	O
–	O
S3	O
launches	O
with	O
the	O
86C911	O
,	O
often	O
regarded	O
as	O
the	O
first	O
significant	O
graphics	B-Architecture
accelerator	I-Architecture
chip	O
for	O
the	O
Microsoft	B-Application
Windows	I-Application
platform	O
.	O
</s>
