All total, there are something like 312 with most of them being European titles as the SMS remained popular there well into the "Mega Drive" days. I'll end up collecting those games, but right now in the US, it is not a buyer's market. Games are priced high already, let alone games collectors are bringing in from Europe. Games like Psychic World are going for over $100.
If you are looking to get into collecting SMS games most are priced in the 20-50 range. I suppose it's kinda pricy, but if you buy one here and there you'll find a lot of fun gems.
I had the SMS as a kid and loved it. Ranking my top three real quick...
1. Rambo
2. Shinobi
3. Thunder Blade
What makes a system like this fun is that you can pop a game in, play for a bit, and then swap another in. So in a way, these games work in concert with each other for a wonderful experience.
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I use CLZ (Collectorz.com) to keep track of my games.
Questions, comments: ljbaby654@gmail.com