The main problem you have is not that you are on a mac but only using the trackpad means any sort of action games are out of the question. I loving Civ 5 at the moment, so I would recommend that.
I recommend Octodad! Using the trackpad makes it almost impossible but it is great fun.
Also, Minecraft.
I am such a dick, I googled 'blaspheme mac game'. Ha!
picked up a little wireless mouse which should broaden my gaming possibilities a bit.
You can also get Xbox 360 controller drivers for the Mac that make the game treat it as if you were playing the Windows/ Xbox 360 version of the game.
What I mean by that is, it maps the correct controls per game for you And it's really easy to set up and use
NB: I have a 2013 MacBook Air and it can run Arkham City no problems as well as the others I mentioned.