I have both Fallout 3 and 2 on my computer, and, while Fallout 3 is clearly superior, I still enjoy the quirky old dog Fallout 2.
Interestingly, bad graphics are far more forgiving in comparison to other games than bad gameplay. For example, while I can play Fallout 3, and then switch back to Fallout 2, the difference is glaring, but at the same time I really enjoy playing Fallout 2.
However, whenever I play Call of Duty 4, and then switch over to Farcry 2, I get incredibly pissed off. The controls for Farcry 2 are so much worse, so less intuitive- the guns are stupidly innaccurate, the aiming is difficult, and, on the whole, the game's actual mechanics feel glaringly inferior. I actually have to wait several hours before I can play Farcry 2 if I've played COD4, or indeed Fallout 3, before I play Farcry 2.
(Interestingly, wouldn't the Fallout 3 engine be an excellent choice for Farcry 2. The added flexibility would seriously improve that game.)