Depends on the show, probably, and the size of your screen and how far you sit from it and how good your speakers are and how much you get into all the background details on shows like The Simpsons.
I don't think early Simpsons is available on BD, but I'd guess that the DVDs are interlaced and don't look great on a big screen. Obviously you can't overcome limitations inherent in source material but you certainly can improve on video compression and things like that.
This is a tough one. Generally speaking television animation is pretty sloppy looking regardless if it was remastered or not. All those screwy pencil lines and cheaply slapped together backgrounds really stand out. As much as I love "How The Grinch Stole Christmas", art design, layout and all, it doesn't "blow up" very well.
Not just animation, after seeing an episode of Scrubs & remembering how much I enjoyed it, I bought season 1-7 from Amazon Marketplace for under £2 a season delivered, & last week I bought Bones season 9 from a charity shop for £2 (I did give them a bit more than that, it was a charity shop). None of those DVD's are on Blu-ray & maybe never will be. All that lot (34 DVD's, I think) for about £5 less than a soundtrack CD from America would cost me!
...oh & the remastered red & blue Beatles compilations for £2 each! It almost hurts paying full price for stuff these days.
I wonder if any of the fine points mentioned would make a difference to me.
I'm the sort who listens to old-time radio, fer gawd's sake.
For the majority of ppl who watch animation it's the voice acting, story and music that interests them. Not the art of the film. But if your interested in the art, the animation, backgrounds, etc, then it could make a difference. My favorite animated film "The Secret of NIMH" looks gawd awful on Blu Ray because it wasn't properly mastered for HD. I prefer to watch my DVD version instead.
