Well for action RPGs, Torchlight 2 came out which you can get for $20 and will definitely last you 20+ hours. Legend of Grimrock is on sale at gog for $7.50. Other great RPGs you can get at gog are Fallout (post apocalyptic), Baldur's Gate, Neverwinter Nights, Icewind Dale (both fantasy), Planscape Torment (really fucking weird fantasy), Ultima (mix of fantasy and sci-fi). You could get any of those for about $5-$10 each.
For strategy games there's Heroes of Might and Magic 3. Warlock (demo is available on Steam). Warlock (the demo is available on Steam). Age of Wonders. Disciples 2. If you're into card games, GoG recently got Etherlords. I've also heard good things about Spectromancer on steam, which was partially designed by Richard Garfield. And, speaking of whom, there are actual Magic The Gathering games on Steam.
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edit: I decided to give Star Trek Online a shot since I heard a good number of the Paragon Studios team ended up there. I've been really surprised with how good the game is, considering how disappointing Champions Online is. The ground combat is bland and basic MMO fare, but the space combat is pretty fun. And they've got a fantastic F2P model (which, again, is surprising considering how bad CO's was). Free players get access to all of the game's content and features. You have less bag space, but since your ship acts as a portable merchant you can buy and sell stuff to then that's not a big concern. The biggest disadvantage that free players seem to get is that you have to buy respecs. Other than that, it feels like "hey, here's our game. Maybe if you really like it you'll buy a cool ship or a key or something? That'd be neat. Have fun." (They do that thing like TF2 where you'll randomly get locked boxes that you can only open with keys you buy with real money).
Almost forgot to mention there's an ingame currency that you can convert to their cash shop currency, so if you get really into the game you can even buy cash shop stuff without paying anything.