Trying stuff for free is my favourite...
I see people have mentioned Broforce and want to add that there was an Expendables tie in promo called Expendabros which is super fun, and free... Or at least was this spring. It's got an old Metal Slug feel to it but different. I find it pretty fun, little comical and for free, gives a good idea of how you like it.
Also as a Shmup Fan, there is a game called Blue Revolver that is super cool, and the free Demo is available and very fun. It's got a Cave inspired feel to it with some interesting art.
Steam had a sale on this past weekend I know and still may... I am trying not to look haha.
I find the PC games that I am drawn to would be awesome on something like a Vewlix or similar. My computer gaming setup is a 32" LG and a Joystick. Old games on old proper cabs seems like a good rule, but once you get into PC games, I feel like there is a lot less rules on what's ideal.