Super Crazy Guitar Maniac Deluxe 3
When I first tried Super Crazy Guitar Maniac Deluxe 3, I was rapidly convinced that it was even more impossible than SCGMD2 (review here). However, once I finished SCGMD2, it was only a matter of time before I would feel compelled to finish the sequel as well, and so I put in a little more effort and finally emerged with another impossible badge. It's not substantially different from SCGMD2, but it's good fun. Anyway, if you're too lazy to read the SCGMD2 review, SCGMD3 is a pretty standard rhythm game: arrows and numbers come from the right side of the screen in time with the music, and you press them when they reach the target zone on the left. Your right hand handles the arrows, which you tap, while the left hand deals with the numbers, which are held for a given length of time.
In the comments section of both games, there is a perpetually running flamefest on whether SCGMD2 or 3 is harder and/or better. Like most Internet arguments, this is terribly stupid; the two games are, like I said, not terribly different; each is hard in its own way. To quickly run down the differences, the SCGMD3 interface is slightly different -- there's now four rows, so each arrow has its own row. This is nice. There are now four hold keys (which are 1-4 instead of ASD by default, although you can also use ASDF if you prefer), which doesn't really make a substantial difference. However, the four hold keys now appear on the rows, like the arrows, rather than between, like in SCGMD2. This means that the arrows sometimes lie on top of the hold bar, which makes it a little harder to read. This is kind of annoying. The interface now shows you how many correct and wrong notes you've hit so far, which is useful when you're going for a perfect. The biggest difference, though, is in the songs. SCGMD3 has a total of 14 songs, and there's no division between amateur and pro any more. The songs themselves are longer -- they're mostly in the 2-4 minute range, which inherently makes them harder. Some of the songs have up to 700 keypresses, which means that even if you have a 99.9% chance of getting any one key right, you still have less than a 50% chance of finishing the song perfectly. So simply from the length, the SCGMD3 songs are more difficult, especially since a lot of the songs have their hardest parts towards the end, which can be really annoying when you screw up after three minutes of perfect play. However, the keying seems to be a little bit easier -- the harder songs, especially, derive their difficulty more from having tricky rhythms than simply throwing a bunch of keys at you. As a result, while the songs can be difficult at first, you can get a lot better with practice faster than in SCGMD2 in general.
As for the quality of the songs, there are more real songs and fewer instrumentals than in SCGMD2. The songs are generally decent, if not great, although the vocals on the songs with vocals are uniformly pretty bad. (Which is not to say that all of the songs with vocals are bad -- indeed, some of them have quite interesting guitar parts -- it's just that the singing is quite mediocre.) The graphics are still very similar -- the crazy stickman is back, although now he floats horizontally when you reach the highest score multiplier; he's also now somewhat better animated, in that you can see him pluck the strings. The game also gives you some aural feedback when you hit a wrong note (which often had the effect of disconcerting me into missing the next few notes too). And, of course, the lag problems are about the same -- I thought that SCGMD3 was maybe a little better on this score, but I was really having trouble with one song (despite having chat muted), and then I switched to another mostly-empty room and immediately got perfect on that song and several others, so it seems that it can still be a big influence on whether you get perfect on a song.
Overall, SCGMD3 is, like SCGMD2, a pretty fun game. If I had to take a side on whether it was harder than its predecessor, I would have to conclude it's slightly easier, but that may just be a reflection of my skillset; I can pick up tricky rhythms more easily than quick key sequences. It is still by no means an easy game; the long songs, especially, you'll have to play through more than a couple of times when you're trying to perfect them. While none of the songs is an instant classic, none of them is terrible, either, and they're generally well chosen and the keying is interesting. If you like rhythm games, it's worth trying it out.