Hmmm. Corporation Inc. is pretty fun. You could also try what thebluerabbit said epic battle fantasy 3. Those are the only long games I played recently.
Corporation inc is pretty fun, but honestly very easy to beat and not that time lasting.
Like Voidy said, definitely both GemCraft games. And if you like Tower Defense games, they're also among the best out there. The Sonny games too, yeah.
The entirety of the Shift series take a decent while to beat if you complete 'em all.
Frost Bite is a pretty fun little platformer that will also swallow a good amount of time unless you steamroll through it.
Amorphous+ is worth mentioning too - a game can take from 5 minutes to forever depending on your skill and the game mode. :P
Dino Run is also a game you can keep progressing on, even if a single run is swiftly completed.