I've been playing Super Mario 3D World with my nephew and a friend who's leaving for the military soon. I was gonna buy Super Mario Bros. 3 but it wasn't on the eShop and I decided, well...what the hell? It's going to be a long, long time before I get to see him again, so $60 for all of us to have a ton of fun for the last few days is nothing. He's usually more a FPS/"hardcore" type of gamer, but as we played through 3D World we were pretty much dying from fun. The insanity and frustration and laughter felt so, so good. There's a level where you have to all control one creature as it goes down a river and dodge and collect tons of things...by coordinating your actions. We were laughing so hard as we were shouting at each other what to do and when. Unfortunately we didn't get to finish the game, so I'm going to have to by myself (or with my nephew), so I don't know how fun it is as a single-player experience.
That said...I am someone who generally detests multiplayer. I do not like playing games with others and it usually is more frustrating than anything, but that was one of the most fun gaming experiences I've had. That is what I love about Nintendo. They are really good at bringing people together to just have ridiculous fun in a room. I can't imagine that would have been nearly as fun if it had online, so I can kinda see why they didn't put it there. That was insane.
Also, I got NES Remix for myself and it's insanely fun too. Seeing Nintendo screw around with their older games and make you do ridiculous stuff is such crazy fun. In particular, there's a "remix" stage of the arcade Super Mario Bros. where all you have to do is clear a stage...but the screen is constantly shrinking and tile-ing so by half a minute in you see hundreds of tiny little screens of the game and it's hard to make out what's going on. You can stop it momentarily by beating an enemy, but only for a moment. Other games are "do x in y game" or sometimes swapping characters into others' games with their own abilities and stuff. It is ridiculous and wonderful.
That aside, my friend brought Diablo III for his 360 and we were playing it. To be honest, it's not great, but I guess it's not bad. Kind of tedious, boring plot, etc. The only real excitement was finding out what skills you were gonna get each level and finding new equipment. How fast-paced it is is probably its saving grace.