I'd rather have high quality 2D Sprites and backgrounds than low-quality 3D, Castlevania for the PSP is one example.

 I'm fine with 2D>3D for some games.

For example I prefer tile based rougelikes to 3D hack'n'slash in general.

For example I like Castle of the Winds more than Diablo. 

For some games 3D is plainly better though, for example shooters. 

I spent 14 hours of super paper mario in 2D.

Diablo isn't 3D. It's 2D in an ismetric perspective. Diablo 2 is also isometric 2D. Some Diablo clones are 3D, though. 

 I thought Diablo was 2.5D at least?

In that it creates the impression of three dimensions? Ahh well, Dungeon Siege then. 

2.5D is 2D gameplay with 3D graphics, like Contra on the PS2. 

 Just looked up D2 on wikipedia, found this quote.

"Battle is conducted in real-time, using an isometric oblique top-down viewpoint (basically, this just means that the game has a set, hovering camera angle, a viewpoint often called "2.5D" because it is between 2D and 3D)"

Of course Wikipedia is a pile of donkey feces so... 

It's all well and good that graphics improve. Nothing wrong with that. For example it enhances COD4. It achieves the tension in the gameplay through use of graphics to great affect. But the 6 hours it takes to complete isnt bad in my opinion. Games that drag out to long for the sake of content can lose their appeal. Theres no problem in mentioning the length in the review but to mark it down and say, it's an awesome game but length brings the score down is ludicrous. Because I bet if there was another 6 hours of single player in there they would say it get repetetive and mark it down for that. My view is The games great in single player, and when you finished that you'll have plenty of months online. Review based on fun. If you can put a disc in a machine and be hooked from start to finish, the game has achieved creating a fun time for you.

There's nothing inherently better about 3D gaming than 2D gaming, or vice versa. They're just completely different.

Some games absolutely have to be in 2D, like Contra, Mega Man, Sonic, Castlevania, Gradius, Geometry Wars, Tetris, etc. etc., and those are all pretty amazing games. I've played 3D Sonics and 3D Tetris, and even that one 3D Castlevania, and they were lame.

Level design in 3D games is always easier, or "dumbed down" to make up for the extra dimension and how it affects the control scheme. For example, the jumps in levels 8-1 and 8-2 of SMB1 are ridiculous, and no 3-D platformer has ever had anything that difficult. 2-D games are just generally harder than hell, when you think of stuff like Viewtiful Joe and Ikaruga and whatnot.

And of course there's a bunch of other stuff that can only be done in 3-D. They both have important places in gaming.

^
However Mario games proved 3d works. Sunshines later levels were some of the hardest Mario moments. And in 3d Shigsy reallised that the need to explore was a big plus in platform 3d.