Great gameplay, unforgettable characters and catchy jingles secure this game's place among the classics.
I'll get straight to the point.
The game is dated, but endlessly fun because of these 3 aspects:
1) Soundtrack and sound effects are unforgettable (especially Ryu's "HADOUUKEN!")
2) It's a very competitive and decisive game. So if you're with friends who like playing, it can get very intense.
3) It takes seconds to learn, but an eternity to master.
The characters are also extremely unforgettable.
Ryu and Ken, the two dragon-punching friends wearing white and red
Honda, the face-painted sumo wrestler
Blanka, the freakishly charming Brazilian monster
Guile, the guy with the flattop and the camo
Balrog, the prize fighter
Chin Li, the chick with the thighs
Zangief, the wrestler who takes practically half of your health away with one grab
Dhalsim, the Indian with the extending arms
Sagat, "TIGER SHOT"
Vega, the pretty boy
T.Hawk, the Native American beast
Fei Long, the guy who pretty much proves that every fighting game needs a Bruce Lee
Dee Jay, his beats are fresh
Cammy, the eye candy
Bison, the dictator
And Akuma, the most overused character in the game. Largely due to the fact that he's extremely powerful and also very easy to use
Bottom line is don't let the old graphics and audio fool you. There's a great game hidden underneath. Although I will say that if you don't have the patience to learn its inner-workings, you'll tire easily and put it down.