The best thing to do right now is to buy a mobo bundled with any game other than Demolish Fist, and then, if you like it, buy it separately as it is very cheap. Since you already have it, then you only have to choice the game coming with the mobo.
I think there are some videos here:
http://www.snk-capcom.com/htm/videos.htm
http://www.insertcredit.com/
My opinions on games:
Demolish Fist: I think it's worth it's current price tag. Just an average game, moderate fun, specially with 2 players.
Rumble Fish: The most original AW game. I've just played the PS2 version and enjoyed it a lot. Of course, you have to consider if it's worth it having the expensive arcade version when you can have the port for a fraction of the cost.
GGX 1.5: Everybody knows about it. Nice game, but again, it's possibly better to have the ports of X or XX.
GG Isuka: Weird game. The controls (a button for turning) kill me. It's also very chaotic with more than 2 fighter in screen. I would rather have the port, as it is much easier to get 4 simultaneous human players in it, plus extra game modes.
KOF Neowave: As good as 02. Therefore, I have enough with my 02 MVS. 02 itself is also ported, and even Neowave is coming to PS2.
Knights of Valour: Some people like it, but it didn't really catch me. Can be a bit repetitive at times.
Dolphin Blue: It's the only one I still haven't played (counting ports). Again some like it, others don't. I think I will like it at least a bit, and I'll find out soon since I should be getting it next week.
So on the end, in my opinion the existance of ports conditionate a lot what AW games to get, as they are very expensive. The 3 oldest games possibly won't be ported (DF, DB, KoV) but the rest, and most of the upcoming important ones (such as NBC) are already ported or will be.
Buying an Atomiswave for home use is not very recommended, it really hasn't that many games nor even good ones. I would wait for something really good, such as NBC before buying it, but that game is going to be expensive as hell, and when it drops in price it possibly will be already ported. Actually when it comes out we should expect more and cheaper loose carts to appear in the market, but I thought the same with Neowave and it wasn't that noticeable, although lately quite more loose carts are on the market, but still pretty expensive.