I'd give 6-8 another shot if I were you. They are quite different, but once you get used to them, there's a lot that's the same.

I'm not sure if I saw it earlier, but Legend of Grimrock was pretty good.

And of course, Might and Magic X is out now and that's supposed to be in the style of 4 and 5. I haven't played it yet, but I heard it wasn't too bad.

I do want to check out MM X soon as well. I wouldn't mind seeing a more modern take on the same genre.

Wizardy 6 is not open world. It's all dungeons IIRC. Wiz 7 and 8 have outdoor areas and are more open in terms of exploration.

Another tip could be the original Bard's Tale Trilogy. The first is only one city and the dungeons below, but 2 and 3 have large open areas and later even time travel. They are included as a bonus in The Bard's Tale here on GOG. If you can cope with the visuals of MM1+2 then The Bard's Tale should not shock you.

Also very recommendable are Amberstar, Ambermoon (Amiga only, sadly) and Albion. They all have TB combat (like a separate game of chess) and open worlds but the outdoor world is top-down instead of FP. The latter two are semi-gridbased in FP-mode. You can roam in all directions but the maps are in tiles (kind of like Wolfenstein 3D).

The RoA-Series (recently on sale) also comes to mind. The first has grid based movement in cities and dungeons, second semi-grid, third more real 3D. World travelling is done on a map screen and largely text based but very well done (for me still the best part). Combat is turn based on a separate battelfield grid.

SSI Gold Box / Buck Rogers? Exploration is first person but then combat goes to a third person isometric(ish) scene, IS turn-based though
I think the realms of Arkadia games do something similar too - not actually got far enough to get into a fight in them to see what combat's like though!

Very good recommendation. W&W is the forgotten Wizardry 8 competitor from D.W. Bradley (creator of Wizardry V,VI,VII and Dungeon Lords).
A true lost gem. This should be on gog.

Review:
http://www.tgeweb.com/ironworks/reviews/wizardswarriors/wizardswarriors-review-081900-1.shtml

The unofficial W&W v1.0 patch is essential and can still be downloaded here:
http://www.tgeweb.com/Ironworks/wizardswarriors/downloads.shtml

now,

Also the >cuthullu< of all Dungeon Crawlers has to be mentioned:

Demise Ascension

This link explains what Demise is:
http://translate.google.de/translate?sl=fr&amp;tl=en&amp;js=n&amp;prev=_t&amp;hl=de&amp;ie=UTF-8&amp;layout=2&amp;eotf=1&amp;u=http%3A%2F%2Fblogensursis.free.fr%2Findex.php%3Fbillet%3D375&amp;act=url

and this review explains, why it is so genial: ->
http://www.bay12forums.com/smf/index.php?PHPSESSID=d6a58dfac9379b70368b31095b7bc3e3&amp;topic=77962.0

more reviews:
http://www.gamespot.com/demise-rise-of-the-kutan/reviews/

Homepage:
decklinsdemise.com/news.php