Here's my favs. All I play runs on a few years old Core Duo Macbook Pro with no crossover. So you really shouldn't have any problems with a new anything.... well, except for anything by Valve I guess. XD
Pac The Man X (essential pac man)
Boxer (DOSBox frontend, easy to use. Just go to Abandonia or somewhere like that for free abandonware games. Or since you have crossover, get some from GOG, install them there, and put the contents into Boxer. :D)
AlephOne (the Marathon OpenGL engine.)
World of Padman (Built on the Quake 3 Engine, arena shooter)
Battle For Wesnoth (Strategy/RPG like Final Fantasy Tactics)
Neverball/Neverputt (Monkey Ball and Putt Putt, plays beautifully on a trackpad)
Secret Maryo Chronicles (Mario in Open Source)
Hedgewars (Worms in open source)
Altitude (Multiplayer 2D plane shooter, completely runs on a keyboard)
BZFlag (Multiplayer tank shooter)
Team Fortress 2 (enough said)
Trine (Action RPG)
Shadowgrounds (Overhead view survival horror)
BSNES (emulator)
Cortex Command (strategy/RTS)
Cave Story (Retro styled 2D shooter)
Frogatto (Retro styled platformer)
Revenge of the Titans (Tower Defense/RTS)
Zen Bound 2 (Relaxing Ambient casual stuff)
Plants Vs. Zombies (Tower Defense by planting seeds)
Tidalis (Match 3 game, Lite version:
Unity Web Player | WebPlayer )
VVVVVV (very retro platformer)
Torchlight (Diablo-like game with steampunk.)
Eets (Remember Incredible Machine? A lot like that)
Machinarium (Point and click adventure)
Samorost 2 (Point and click adventure, First one:
Samorost 1)
Pangea Arcade (It's in the App Store)
Oh, here's some needed other items too:
ClamXav (It's a virus scanner. Because what's in the app store sucks, and just in case.)
The Unarchiver (Use it, and it unpacks literally anything you throw at it. So much better than the default archive thingy.)
LibreOffice (Do you want to pay hundreds for your Office apps? Didn't think so.)
Seashore (think Paint with a few more items in it.)
Transmission (Best Torrent app you can get.)
OK... I think that's it after tons of editing. If you want links (especially to the free ones) let me know.