Yeah I played WSC before, don't own one though. I have an unopened Final Fantasy II sitting among my Famicom collection just cuz it's cool to have. Hey I got an English translated ROM so that's good enough.
However, I have played Guilty Gear Petit, and that's the ONLY Wonderswan game I've played on the actual hardware. I personally don't like the system for several reasons:
1. It's not backlit and you have to line up the solar system to get the perfect light like the the Game Boy systems before SP. When night falls and you're on a road trip, you're pretty much fucked.
2. The D-pads are not joined. So it's sorta tough to do diagonals. Heh, that reminds me of when before PS1's debut 10 years back I used to think that's how the pad handled.
I find it very weird though that on some WS games, particularly the old B&W ones, some stages have funny screen ratios, so you have to either hold the system vertically for a couple of stages, or sometimes horizontally. That's why there's way too many buttons on all angles of the WSC.
To tell that I'm not bashing it and each individual's judgment is different, I'll have to be like Reading Rainbow and say "Don't take my word for it."
Other than that as far as games go, I'm sure alot of the remakes of different games such as Square's FC/SFC games, and Golden Axe are at the top.