I'm going to go the other way from everyone above here and go for Animal Kingdom.
Whilst IOA is undoubtedly an amazing park, it feels very transient. Like in 25 years time Animal Kingdom could not have changed and would still remain an amazing day out, whereas it feels like IOA is more of its time. Every day at Animal Kingdom is such an amazing day out. Yes there's not many rides, but in my opinion Flight of Passage beats any screen based ride at IOA, and Expedition Everest, whilst not as thrilling as say the Hulk, is a criminally underrated ride. But Animal Kingdom its the full experience. The uniqueness of Kilimanjaro Safaris. The shows (Lion King is basically West End quality!). The pop up entertainment, African Bands etc. The food - Tiffins must be one of the top in park dining experiences worldwide, and Flame Tree BBQ is awesome. A day at AK always feels so chilled.
Thats not to say IOA isn't good. I find it very good. The rides are excellent. But to me it doesn't wow me in quite the same way as Animal Kingdom.