If you can't get the gamepad controls remapped, KB+mouse should do just fine. And you don't have to exercise. Eating restores your health but beyond that there's no need to do that either, unless you wanna make your character really fat. Which you totally should btw, how many actiongames lets you be a fat guy after all? Um... actually now that I think about I guess Saints Row and quite a few other games that let you customize your character does, but when GTA SA first came out it was pretty fresh. Some people say the game was breaking new ground in letting you play a black character, but that had been done before, in Urban Chaos, Shadowman, and probably some other games as well. The real breakthrough was letting you play as a big fatass.
And yeah, the game's graphics were dated already on release since it uses basically the same engine as the several years older GTA3.