Pretty common, although the 210 turns up more often here in the UK, and the 450. Worth much? No. The common one. Zelda's Adventure is the rare one. Unfortunately, they're all in a bit more demand now with Zelda collectors. It means that Wand of Gamelon and The Faces of Evil will go for more than they used to (sod all, basically)... but it doesn't stop all three of them from being dire games with sluggish controls! Yeah, as mentioned, really. 7th Guest was good, but dated. Lemmings, Mad Dog McRee, Micro Machines, Myst, Shaolin's Road. The Mario games, I guess. The board/card games were OK. I liked Voyeur, but it had several flaws. One is the premise of the camera running out of battery in your hotel room, so you have limited time... then have to charge it. Uhh, just plug it in FFS?! Also, the game randomizes what you see each time... and it's complete luck as to what you see. Sometimes you may piece clues together and have a good idea "whodunnit". I remember a time playing with my friend - we were clueless right up to the very end... when we witnessed the murder! By the way, the CD-i is not a rare format at all. It was a weird edutainment device incorporating game console, learning tool and a Video CD / audio CD player. It even had a modem available. It was the sort of thing parents thought would be a good idea, but due to its weirdness, it never got used and you'd see plenty at boot fairs going very cheap. If you want more information on the system, check out www.philipscdi.com.
Eh, sold it at the local games store with all the games for $78. I could have gotten more, sure, but it was alright considering I paid $17 for everything. I went back into that thrift store today and saw a few more CD-i games (complete with the tall boxes) for $3 a piece. Nothing good but Tetris, though.
Doom 3DO is abit of an oddity. It had all the potential to be a fantastic game. The 3DO could probably run it just as good as a PC could given time to polish however it requires to be shrunk to a ridiculous size to even be playable with the framerate. The graphics and music however are kickass. I'd like to see a homebrew project refine it.