Well the important thing is (and the reason why I decided on 3gb) is because when you are heavily modding Skyrim, you can easily go over 2GB vram if you have enough texture packs installed (just ask Neovalen). While the extra memory may not come into play for other games, it does come into play for Skyrim with tons of texture packs.
This is most definitely the case, with just Beth HRDLC (half normals) + SRO 2k (unoptimized atm) I can hit over 2GB VRAM around Windhelm. Most places lower but Windhelm is a killer for resources and where I am doing the majority of my stress testing. I haven't even gotten to weapons, armor, characters, FX, etc yet with my latest round of testing. For modded Skyrim I'd certainly say 3GB is a great thing to have.