So I got myself Super Smash Bros., F-Zero X and Alien Crush for the PAL Wii Virtual Console.
While the two N64 titles look as blocky as I remember them, they play pretty well. Emulation-wise, good thing the screen resolution has been upped to 480p, so the trademark anti-aliasing blur of the N64 isn't as hard on the eyes as it was back then. The background music has the usual issues of emulated N64 games, with slight stuttering when loading the next menu screen, level or area. But nothing gamebreaking - I've seen N64 emulators on Windows PC doing much, much worse in terms of crippling the music and placing ugly seams on semi-transparent 2D objects. Try PC emulation of games like GoldenEye 007 to see and hear with your own eyes and ears what I'm talking about.
Both F-Zero and Super Smash Bros. are PAL versions, so they run slightly slower than their NTSC counterparts and have slight horizontal black screen borders. But since they are decently optimized for 50 Hz, the difference isn't as much noticeable as when talking about non-optimized games - they'd look, feel and sound horrible. E.G. take a look at videos of Sonic 1 (Mega Drive PAL) and Castlevania 1 (NES PAL) to see a PAL conversion gone awfully wrong, Nintendo didn't bother to fix this for the Virtual Console release.
Turbografx-16/PCE games are NTSC 60 Hz all the way even on the PAL Wii Virtual Console - NICE!
I didn't noticed any input lag whatsoever on all these and the other VC games I got so far. Which is quite remarkable, cause usually I'm quite allergic to even the smallest of lag. Good job on that.
Super Smash Bros. character models are quite low on the poly count, noticeably lower than you know them from their original games. E.g. compare Smash Bros.' Donkey Kong, Super Mario and Link to their counterparts of DK64, SM64 or OOT. Made my head scratch why Nintendo did this in 1999 and still does make me continue scratching it 18 years later.
Occasionally, the Wii VC version of Smash Bros. may crap out sound wise, producing funny noises for both music and sound effects. Playing against Master Hand or resetting the game usually fixed this for me.
Super Smash Bros. does play well with a GameCube controller, familiar button layout to Melee. You need to press down the analog shoulder buttons all the way to the "click" for blocking, though. F-Zero X is better played with a Classic Controller Pro, due to the digital shoulder buttons make destroying opponents easier, since you need to double-tap them for tackles and spin attacks.
Devil's Crush is just Devil's Crush. Pure awesomeness. I'm glad I tried it! Nice graphics, good music, great level design and the gameplay has stood the test of time very well. The emulation is quite good, apart from the usual graphics change regarding the pentagram. Being able to save the gamestate anytime and continue playing another day is what I find very convenient. I used a NES classic controller attached to the Wiimote for this game.
EDIT: Corrected typos and added some doodads.