This is a random one, but one that I think could've had a lot more potential if they could've pushed it out longer, and that was Shane McMahon and Test. Granted, I don't think either of them are great performers, but it was a feud that I think could've really gone a lot farther if they wanted it to. I still think it was a good feud, but just too short.
Another one that had a lot of potential but I think was just kind of short was Big Boss Man v. Nailz. This was a good feud based on revenge that just didn't go far enough.
My favorite emotional feud of all time, and I'm surprise this one hasn't been brought up yet is Hulk Hogan vs. Andre the Giant. Andre was a friend of Hogan's for years. Then, on Piper's Pit that one fateful day, for what was seemingly no reason, Andre just ripped the cross and the shirt off of Hogan. Not only was this a great feud, but it was a feud that lasted for over 2 years. Of course, there were only one or two PPV's during the year, so you could really build things up, but that was just a great feud to me and something that really drug me in.
Here is another feud for you, that really never took off, but had a lot of potential. Randy Savage vs. George Steel all over Elizabeth. Lot of potential, just kind of fell flat for me.