This will be an interesting one, as everyone has their own opinion and preferences, I'll share mine
MK:
3:00 parade - Liberty square, where they take the turn in front of Hall of Presidents. You catch it early on so you can go do other stuff once it passes and you get to see it coming and going.
Spectro - Same spot as above, instead this time it will come from the hub over the bridge towards you. Actually like to sit more towards the bridge for this one. Seen it on Main St a few times, its just SO crowded and hectic to see it there.
Wishes - Now this is why people LOVE me

I watch Spectro on one side of the park, and book it across the hub to watch Wishes. I LOVE to sit at the walkway to Tomorrowland, Tink flies over your head and if you get the right spot, you can sit with the fence of the garden behind you and just relax! Its a GREAT view. Also watched from along Main St before, so crowded and from in front of the Train Station and it seems obstructed. LOVE the walkway to Tomorrowland
Epcot:
Illuminations - never really a bad spot as long as you don't have a tree blocking your view or you arent sitting upwind (smoke). When walking around WS you'll see some patios that are down stairs along the lake. SOMETIMES these are open to the public and are a GREAT place to sit for the show.
MGM:
Parade - Never seen it there so I won't even venture to guess
AK:
Parade - Don't there there is a bad spot, we like to sit in front of the shop thats right there before you hit the bridge to DinoLand. If you come in the park, hang a right at the tree, sit to the right, kind of across from the Tough To Be a Bug FP machines. We always get a great view and good interaction there. AND its an easy exit after, we are usually done with AK by the time the parade is over.
Enjoy!!!!!