The first question was pretty good. Can we make it two in a row? I think we can...
What I am looking for in an RPG is a cool idea.
When I find a new RPG, an old one I've never tried, or even an old one I haven't played in a very long time, what intrigues me the most is that it has something about it I either haven't seen before or haven't seen done that particular way.
I think this may explain my love for certain older RPGs and why I tend to have little interest in the latest version of them. I still play Champions 4th Edition, Ars Magica 3rd, and Pendragon 4th. I prefer Changeling: The Dreaming to the Changeling: The Lost. Why? Because the later versions of these games aren't doing anything new or interesting. They are like the rebooting of movies. They rarely bring anything to the table that is better or more interesting than the original versions.
Now certainly there are improvements in the mechanics, better art is some cases, or the like, but since rule mechanics are a secondary (at best) concern for me and art is both subjective and I prefer to come up with my own, a shiny new paint job on the most recent model rarely makes me feel the need to trade in my old, classic car.
There are exceptions of a sort.
Star Trek Adventures for example is a very different game from Last Unicorn's Star Trek RPG, which is itself quite different from FASA's Star Trek, The Role Playing Game. I like each of them for somewhat different reasons, yet the key to why I periodically switch from one to the other is that they each bring with them something different. Yes, they are all Star Trek, but each takes a different attitude towards the Star Trek universe and it is those attitudes that intrigue me enough to own and play all three.
Basically, the idea of a Star Trek RPG is not new or different but the approach each game takes is unique, and therefore worth reading and playing.
Bonus Answer: I love games where the fluff and the crunch match. I definitely look for that in a game or more accurately, look to see if it has that element or is missing it. I despise, 'Elves are inherently magical beings', and then nothing reflects this in the write-up of Elves. 'Magic is a dangerous force if used improperly", and...nothing about what happens if you misuse it, whether or not you really can, or anything of the kind.
Ugh. Save me from games that tell a good story and do nothing to back it up in the mechanics.