Wizardry (the series as designed by Sir-Tech)
I have much more experience with the 1-5 era than the Dark Savant era and my general impression is that they (in paricular Proving Grounds of the Mad Overlord) are probably one of the Top 5 influential games of all time. They have definitely aged but I think if you are at all interested in game history then they are required playing. The Dark Savant era is more of an interesting case where you can see trends and design ethos of mid/late 90s Western CRPGs. Though I've only really played 8.
Wizardry (the Japanese take)
Honestly I find most of them kinda samey and stick way too close to the source material of the ones I've played.
The one exception that comes to mind is the Wizardry Gaiden series by ASCII and in particular Wizardry Gaiden IV: Throb of the Demon's Heart for the Super Famicom which combines the races and classes of the Dark Savant era with classic Wizardry gameplay. Kind of a dick, but what do you expect? That series did spinoff into Class of Heroes, but I really didn't gel with those.
Wizardry-likes aka Blobbers
I love Blobbers. Especially blobbers with full character customization. Actually thinking about it, I think almost all the RPGs I've been into recently were blobbers.