Ugh, Street Fighter 1 was horrible!
Although, it was fun to watch folks play the "two big button" version (one punch, one kick button, each the size of a pancake. Depending on how hard you hit each, you got a jab/strong/fierce... heh!)
PS. Damn you, SF1 Sagat!!!
Anyway, I'm partial to SSF2T and SFA3. As StaticX mentioned, SSF2T is the most balanced, and thus the most fun. Of course, you should be playing versus another opponent, never the CPU!