Grand Thieft Auto San Andreas
The most epic game in series by amount of gameplay features. Quality difference is much bigger than between GTA Vice City and GTA 3, so modding of graphics have reason. First version of ENBSeries was developed for this game 3 december 2007 and had SSAO with SSIL only. Game is very popular for modding and even now many peoples playing multiplayer version of it (SA-MP). I like GTA Vice City much more, because it's more "romantic" and atmospheric for me, but GTA San Andreas is more rude.

Different versions of the mod have own visual look, latest have not finished reflective bump (dudv environment bump mapping) for rainy weather in the very old versions of the mod and these days it's not much usable, when latest versions allow to make many more effects in the external shaders.
Some mods working improperly with SAMP, because several functions are hooked by SAMP and not return proper result to ENBSeries. Also some servers replace shaders, so if you have issues with vehicles, they are invisible or look weird, that's must be the reason. Same about water, reported as problem several times as well.

You may see comparison screenshots from this mod and vanilla game in the gallery or on the gtaforums.com web site or youtube. Of course everything can be modified by yourself. There are some popular presets made by players, i recommend to use them, just take the latest d3d9.dll from my mod and shaders from their works.

v0.430
v0.306
v0.248
v0.158
v0.076
v0.075c3
v0.075s for old SAMP
v0.075
v0.074h10
v0.074g
v0.074f
v0.073a