Only thing is to catch the Steam sales... picked up Mass Effect 2 in the EA weeks last week, etc. Crazy good value if you catch those 75% off.
At the Steam christmas sale last year I actually got a few collections of old games I wanted to replay. Monkey Island, Loom, The Dig, Indiana Jones Collection, Space Quest Collection, Kings Quest Collection, Darwinia, Eufloria, Osmos, Samorost 2, World of Goo, Machinarium, Missadventures of MR Winterbottom, Defense Grid, Trine, Shadowgrounds. Can you tell I love puzzles and adventure games
Also, great platformers, with a new take on it like winterbottom. But among all those adventure games above, thats a HUGE load of hours right there. Especially since i never played every single game the first time around. But Space Quest definitely needs a new playthrough.
Also, I just love games with great art. Machinarium, Eufloria, Trine...