Dungeon Explorer is definitely the superior game. I think Neutopia has some fine music and atmosphere, but doesn't hold up the imaginative standards set by The Legend of Zelda. The first three Zelda games have a soul.
I loved Zelda and LttP both (and the two Neutopias!), but when it comes to these types of games, I always pick Crusader of Centy first. A lot of people will disagree with me, but I love the FM tunes and the way the game controls. It's a reasonably long game and has lots of cool little hidden surprises and funny remarks from NPCs. To me it feels like a perfect mix of the depth of LttP with the lighter action-first vibe of Neutopia.
Crusader of Centy is a game that has always eluded me. I have never seen it for sale anywhere (aside from ebay). One day I hope to see what all the fuss is about. I refuse to emulate games in most cases.
When I started high school, I had given up on games for a couple years (girls, guitar, etc), and passed my 16-bit systems down to my little brother. By this time Genesis games were starting to appear at yard sales, swap meets, and thrift stores pretty regularly. My parents bought him a box of games that included Crusader of Centy. I saw him playing it and got hooked right away.
After I moved out, I was lucky and bought mine for cheaps, locally if I recall, but yeah, this one fetches a pretty high price online. I love the game and considering how short of a run it likely had, I'm not surprised that it's priced more than other games. But it's disappointing to see it going for such a high price since I always hear from folks who say they've never played it.
I don't care much for emulation either and that's why I haven't played any of my recent TGCD purchases or some of the more expensive TG games (MC, Tonma, Bonk 3) so I feel your pain. I imagine you'll enjoy it when you eventually get the chance.