Which Arcade game, out of these choices, should I buy?

 Please don't recommend any others as I probably already own them

The Maw first and foremost because it's just a lovely game in every single aspect.  However, should you have a decent PC I'd recommend getting The Maw on Steam and buying Space Invaders Extreme via XBLA because it's just that good.

I went with Pac-Man CE. It's a great remake of Pac-Man.

FUCK YEAH, IKARUGA. 
 
Welcome to BULLET HELL!