I quite liked the remasters of Kingdom Hearts (only played 1.5 so far), and found it to be very much worth my money. Actually, I think Square Enix puts out pretty good remasters in general.
My only problem with Remasters is that if it involves a collection, that sometimes more effort is put into one game than the others. Better sound, redone themes/models/textures, added gameplay tweaks, etc. Going from one version that you can tell was worked on a little longer is annoying as I prefer an even playing field for every game on the collection as much as possible.
But there are remasters out there that aren't so well done. I don't usually play them that often, so I can't say which ones are considered "bad", but I'm sure there's a list somewhere out there on the internet.
I do sort of wish more remasters wouldn't mind tweaking existing cutscenes or adding new ones/fixing some old ones. Sometimes games go on for X years, and I'm sure some of them couldn't account for the direction they would eventually go in. It'd be nice so see a better consistency. However, that's really just something of a wish of mine, and not one that really determines if I get a remaster or not. I'm sure there is a limit of how much time and money they are willing to spend on a remaster of a game/set of games.
Sorry to hear about your disappointment with Halo though.