We are vegetarians, so YMMV, but our current picks are:
MK: none (we hope on the Monorail and go to The Wave at CR)
Epcot: Via Napoli/La Hacienda de San Angel
HS: Mama Melrose
AK: none (we drive over to AKL and eat at Sanaa)
FWIW, our answers would've been different 5 or 10 years ago...menus change fairly often, and it may not actually be true, but it seems like when we find a favorite dish somewhere it's doomed to be discontinued, lol.
Also...our family no longer eats at buffets. On a trip to Las Vegas about 5-7 years ago, there was a norovirus outbreak whose source was identified as the buffet at the Hard Rock Hotel. As you can imagine, given how many people travel up and down the strip for food/entertainment, it spread from there. DH and I were at the Four Seasons for what was supposed to be a romantic anniversary trip, and we ate at the buffet at the Wynn. I got sick but he didn't. I have never been sicker or more miserable in my life than I was when I caught norovirus...couldn't leave the hotel room for the entire trip (we ate at the Wynn the first day), couldn't get on the plane to go home, and had to use the hotel doctor to give me a shot to ease the symptoms so I could survive the (delayed) plane ride...then was still miserably sick for 4 days afterward. From that day forward, I've sworn off buffets. I know it's irrational, but I just can't do it...maybe someday I'll get over it, because I've heard that Tusker House has a fabulous buffet for vegetarians and I'd love to try it! Maybe in another decade or so the symptoms will be erased from my mind and I'll be able to try one again...