Well that's all down to personal preference, don't you think? There are so many ways to pick games you might like - I've experimented with a ton! - and the tried and true method still works the best for me: looking through screenshots, playing a bit of the game, and adding it to favorites; or in this case, putting it on your N900. Of course, that doesn't guarantee the game will play, or play well enough, on the N900, but the only way to know is to try. Experimentation is half the fun.

So try this.

Go get MAMEUI here
http://www.mameui.info/

and get the screenshots (aka titles, or "snaps", the name of the folder you'll put it into) here
http://www.mametitles.com/

Install MAMEUI and put the snaps in their proper folder, run MAMUI, and as you scroll through the games list, you'll be able to see a screenshot of any game you might be interested in trying. And you'll also have the name of the rom you'd be intersested in right there in front of you.

Of course, if you do then want to get the games to play, you'll have to figure that part out on your own, but it shouldn't be too difficult. Again, as usual, there are easier and harder ways to to that, too.

***And please note, mods or anyone else, the links above are NOT to rom files, they are just to the MAME software itself, and to snapshots of the games that MAME currently runs - nothing more***