I've been growing my MVS collection pretty steadily over the last few months. I'd say I only have ~8-10 games that I'd like to get. I already have my "grails" so to speak (Last Resort, Pulstar and Blazing Star), as well as some of the games I paid a pretty big chunk for. I don't really regret it though, because all of the games I've bought, I genuinely enjoy and play regularly. Shooters have always been my favorite, and probably will be. The Neo has a really solid number of great shooters, so I've tried to buy all the ones I really like. Problem is, like others have said, they're all usually really good. I have a 161-in-1 cart, but I much prefer the original cart over a multi. Plus, I can save my high scores etc since multi's like to reset the backup ram every time
I'd say the carts i'm looking for still are;
Alpha Mission 2
MOTW
Ghost Pilots
Robo Army
Strikers 1945 +
SVC Chaos
Shock Troopers
Shock Troopers 2nd Squad
Other than those, I have all the games I want and actually play. I've got about 50 carts so far, so I'm pretty close to being "done". After those, There's nothing really else that I can honestly say I'd consistently play.