I enjoyed 4 enough to do a second no alerts run through. It does a good job of tying up most of the story threads and earns its emotional beats much more than 5.
I've just started watching this Let's Play of it, on the strength of their brilliant LP of Rising: Revengance
Never got around to playing 4, is it worth it?
I've pretty much decided that it's not, aside from the nostalgia factor of going back to Shadow Moses.
Spyro remaster would be awesome though, my favourite platformer of that generation (aside from Croc)