1. This is old hat (more than 10 years old), but having some kind of robust conflict resolution mechanic which is NOT based on character abilities can be tremendously helpful.

Sometimes you just wanna know whether your character falling over into the mud could solicit sympathy from the Princess, you know?

You can’t get that kind of thing from a to-hit roll, but in many games it can spice things up and help us move past a disagreement and back to the game.

2. Clarity of Creative Agenda in the game itself. Whether it’s the design of the game rules or just the orientation provided by the text, some games are maddeningly un-self-aware, and refuse to tell you the point of playing the thing. (“You can be anyone you want and do anything you want! Game X allows you to do it all!” That gives you very little help when you’re trying to figure how to make your game better, or which bits to focus on and which bits to leave out.)