As long as they meet the height requirements (and are adventureous)-
My 4 year old (4.25, so closer to 4 than 5) loved BTMRR, Splash, and 7DMT. Those were her favorites at MK. She was fine on POTC and asked to do HM again. I would also pick PPF because the line for that can get quite long. While she liked everything, the first 3 were definitely her favorites.
At Epcot, she loved Soarin', Turtle Talk, the Little Mermaid ride, Malestrom, Test Track, and Living with the Land. For FP, I would do Soarin or TT (since they are tiered) and Malestrom if you are interested (because the line gets really long- I saw it reach 60 minutes.
DHS was a bit more tricky for us. Definitely TSMM for #1. She rode TOT and was willing to repeat it, but only once...she didn't like going up and down (she didn't find it too scary). All of the shows are good, but I don't know if I would FP them, just because you have to wait to get into the theater anyway and most shows have plenty of seating.