1) Ultima False Prophet SNES
2) Ultima Avatar NES
3) Order of the Griffon TG16
I really like the combination of overhead maps, first-person dungeon crawling, and turn-based battles in both Ultima IV and OotG.
---Ultima games---
Ultima IV on SMS is a little truer to the computer original in that you can buy food (oh boy!) and pick conversation topics, but the graphics are rather painful. The updated graphics and things left out in the NES version really are an improvement, IMO.
The Nintendo ports of V and VII are bad. I beat III (Exodus) when I was ten, but it hasn't aged well. The Runes of Virtue Ultima games are puzzlers, not RPGs.
---SSI games---
Warriors of the Eternal Sun on the Genesis plays almost exactly like OotG, except battles inside dungeons occur in real time, in 3D mode.
I haven't played much Pool of Radiance on the NES yet, but it seems quiet good and I remember friends getting really into it back in the day. The battle system is overhead, turn-based like OotG.
Eye of the Beholder SNES is entirely 3-D dungeon crawling with no overhead action or towns. I like it, but having to go fetch and reuse arrows and sling stones sucks.
FYI, Eye of the Beholder and Pool of Radiance use the "Advanced" D&D rules, so you have more flexibility in the characters you create - gnomes, characters with two classes, elves who don’t necessarily cast spells, etc.
---others---
I played Might and Magic III on Macintosh back in the day. It's a great game. I really like the randomized magical items that appear, but the quest got too long for my tastes. My brother sunk hours upon hours into it for weeks or months before beating it (and he had the several-hundred-page strategy guide). I don't know which console version is best.
Times of Lore NES isn't exactly good, but it's cheap and it kept my interest long enough to beat it. It's a rules-lite RPG with a Hydlide-esque battle system. All of the action is overhead in real time. The enemies are boring and quickly dispatched. It has a nice day-night cycle and I enjoyed all of the free-range, wandering around and figuring out what had to be done. There are only a few points where a walkthrough is necessary.
Dungeon Magic on the NES is a first person RPG that requires a lot of mapping. It’s fun, hard, and has a cool magic system. The sound sucks/is nonexistent. I made it quiet far, but never beat it.
Bard’s Tale and Wizardry look sweet, but I haven’t played them yet.