Here's my list of what has been impressive, and what has been not so-impressive. I certainly haven't played all of these re-releases, so jump in.
Top Notch:
OK, Bluepoint seems to take the cake, with their "remasters".
God Of War Collection
God Of War Origins Collection- This actually may be the most impressive one I've seen, considering they were PSP games.
I'm VERY happy that they are doing the MGS and Ico and SOTC collections(they're not doing PW though). Anyone know if they're doing the ZOE collection, as well?
Impressive:
Ikaruga- looks about as good as I could see it looking.
Rez HD- Same goes for this.
Outrun Online- I haven't played enough of this to truly know, but from what I've seen, it looks top-notch.
Strong-
Tomb Raider Trilogy- Flat out, all I've played is Anniversary(since it's the only one I liked in the trilogy), but it looks really good to me.
Good Effort-
Radiant Silvergun- Really nice, for doing a Saturn game. I know they have a small team, so they couldn't go "all out", but it does look a little odd at times. The jaggies are really toned down, but they couldn't cover up that those were 32 bit polygons. On an SDTV though, it rocks. Except for that 4:3 crap.

Slapdash-
Resident Evil 4 HD- This isn't HD. It's just upscaled. I'm torn as to if it looks a little worse, or better on an HDTV, than the old GC versions. They were really lazy with this one. On the bright side, it looks GREAT on an SDTV. But that wasn't the goal, and it deserves way better than this. If I can play freaking Chains Of Olympus with no jaggies, I should be able to play RE 4 with no jaggies. No excuse, considering Capcom is a really big corporation.
Well, what have you guys seen?