On a personal level, this is easy for me. Muta. His character performance was captivating, his matches during his prime were quality, he was doing shit that no other heavyweight was doing back then, and his feuds with Sting and Hase are two of my favorite ever.
Objectively, though, I think it's a lot closer than that. Muta's late 80's to early 90's run in the US and mid 90's run in Japan was fucking INSANE in terms of match quality and showmanship. He was also doing crazy shit for a heavyweight back in that time frame; his moonsault (still one of the best I've ever seen), planchas, missile dropkicks, handspring elbows, . He also had a better, constantly evolving gimmick and portrayed it to perfection.
Liger, on the other hand, was even more innovative and cutting edge than Muta, was probably more influential to a wider number of wrestlers, and remained a top notch worker for longer, so you've got to factor all that in. While I'm partial to Muta on a personal level, I'm not sure one could objectively place my favorite Muta feuds any higher than Liger's rivalries with Pillman, Benoit, or Otani.
So many great matches out of both guys. Speaking of Muta, I wish Ambrose would stop doing that power drive elbow. Ambrose is a good worker, but he doesn't even come close to executing that thing like Muta used to.