I literally just posted this on someone else's thread, But you might need it too.
Garry's Mod Portal 2 Battleblock Theater Civ 4 & 5, 5 is better but 4 is cheaper and less laggy Battlefield 2 + FXAA and Bloom mod Deponia is written by Matt Groening and is hilarious, But still interesting. To The Moon is a art game done right. You have to have some patience though, It doesn't get good until 1-2 hours in. Bastion Half-Minute Hero:Super Mega Neo Climax is a parody of RPGs, But I found it great. Titan Quest Command & Conquer 1 for DOS. Use DOSBOX or something like that. Still holds up today. Mirror's Edge is a little demanding, But I got 30+ FPS when I played it. Burnout Paradise:The Ultimate Box. Demanding, But its so fun I don't care. Better than the originals. Terraria is fun in short doses. Minecraft. Its demanding, And that's my main issue. I've had hours of fun on servers though.
Here are some DOSBox games to try out also.
The Lost Vikings Commander Keen 4 The Oregon Trail. Its educational, But its hard as heck. Zork 1, 2 and 3. Simcity 2000
Windows 8 - AMD Dual-Core E-3000 - 4 GB RAM - ATi Radeon HD 6310 I will change this sig when Gabe posts a picture of himself eating a Twinkie.