They are approaching 100 ACA NeoGeo titles, and they have published around 25 Arcade Archives titles (including some from Nintendo). Nintendo stuff aside, most of that stuff is also available on PlayStation 4. But to me, Switch feels like a better place to play it. If you want to see what all is available, the "A" listings for Nintendo Switch here on this site are a great starting point, since all of Hamster's stuff for the system starts with that letter. Most weeks, Hamster releases two new games: one NeoGeo title and one general arcade offering.
"Too often we enjoy the comfort of opinion without the discomfort of thought." - John F. Kennedy on reality
"What if everything you see is more than what you see--the person next to you is a warrior and the space that appears empty is a secret door to another world? What if something appears that shouldn't? You either dismiss it, or you accept that there is much more to the world than you think. Perhaps it really is a doorway, and if you choose to go inside, you'll find many unexpected things." - Shigeru Miyamoto on secret doors to another world