hm.. cave story.
played it two times to the end.
I like the sprites(the smaller ones), even im not a big fan of detailess simple shading.

I think that cave story got the most votes more because it has some kind of
strange popularity rather than outstanding pixelart technics.

Tiling looks on some places to obvious.
Here and there is strange aa going on. some sprites and backgrounds have some,
others not or only on parts.
takam already mentioned the one eyed metalblock thing,
thats pure lazyness.

And the ending pictures are more oakaki(or somethink like that)
than real pixel work (imo). 

thats all of from a artistic point of view.
The game its self plays really good and its good balanced.