Unfortunately, the Sega CD Dungeon Explorer game isn't anywhere near as good as either one of the TG16/CD titles. It has nice graphics and music, but the gameplay has some serious issues. They dropped the first DE's "you level up by beating bosses" system with an experience-based one, but it's balanced badly, so exploiting it is not hard, and even if you don't the game just isn't as much fun as it should be because of the messed up balance. There are also fewer characters to play as in SCD Dungeon Explorer; there are only six, and they're all male too. No unlockable characters this time. At least the game does have nice graphics and sound, four player multiplayer, and it is a new, exclusive title, but other than that... really, overall I'd rather play the first game on TG16 again, instead of the Sega CD game.
Tehe game is also odd in that it's a Japanese-developed game that was only released in the West... I know that in 1995 when it released the Sega CD was dying in Japan, but still, it's odd that it wasn't released at all. I mean, the SCD did have a handful of releases that year in Japan, but not this one. With other games like that it's easy to see why, because they're TGCD ports (Cobra 2, Snatcher, Lords of Thunder), but this one isn't a port.