Going to try something different -- rather than revealing the tracks people have already guessed and giving hints for the ones people haven't, I'm just going to give hints for all 20 tracks and see if anyone is able to guess any that way (whether or not they've already been identified elsewhere). The track list reveal will come much later in the week.
01: This is from a multi-platform indie release. The melody is the main theme, though the style is obviously Super Mario Bros. -- and unsurprisingly, that style is intentional, as this is a special track used only on Nintendo platform releases. Other releases had tracks that sounded kind of like Ghosts & Goblins, or even Indiana Jones.
02 (identified): This one is hard to give hints for other than to say "try to guess from the style." Because the style of music in this game is very distinctive, and reminiscent of previous works by the same composer (and for this game's spiritual predecessor).
03: This is another one that can theoretically be guessed from style alone. It's one of the few original tracks in the OST represented, as much of the rest of it consists of arrangements.
04 (identified): This one should sound familiar to you. If it doesn't, chances are you won't guess it... but if you've played earlier games in the series, chances are this is the very first one you figured out. Probably the easiest on the list.
05: It's hard to give a clue about this one without completely giving it away. Let's just go with, it's the only game of its genre represented on this entire list, and only one other game of this genre was represented on previous lists.
06: This track was used in the launch trailer for the game, and is actually the second half of its main theme.
07 (identified): This is an extremely new release, but a very popular one -- probably THE most popular on its platform.
08 (identified): This track was composed using actual 8-bit synth capable of being played through a Famicom system, for authenticity.
09 (identified): Most of the soundtrack to this game is 8-bit, but not NES-style 8-bit. The game, and its soundtrack, were designed to emulate old-school PC titles.
10: This is from a relatively recent PC release covered by RPGFan, but not RPGamer.
11 (identified): This is another one where the style is a dead giveaway. A slightly different (earlier?) version of this track was used in one of the many trailers for this game, and it shares a developer (and game engine) with one other track on this list.
12: Think about what language this track is sung in, and what style of music it is, and try to figure out what kind of game would use a track like this. The answer may come to you.
13: I don't really like this soundtrack. The original versions of these songs had a lot more pep -- these arrangements are too slow and ambient for my liking. But they are at least accurate to the originals melodically...
14 (identified): Does the melody sound familiar at all? It's actually a really famous song. And some might find its usage in this game kind of offensive, but that's also sort of the point.
15 (identified): This is the main theme song, used in all the promo materials for the game. There's a Japanese version as well, but the developers went to great lengths to localize this game for the west -- some might even say TOO far.
16 (identified): You probably noticed that this is a jazzier version of the classic song "Moon River." There's really only one game released this year that would pay for a famous song like that, and arrange it in such a fashion.
17 (identified): This song was included almost solely for irony value. It's not indicative of the vast majority of the game's soundtrack because most any track that IS indicative would've been an absolute 100% dead giveaway.
18 (identified): Yes, those are Vocaloid voices you hear, but no, they're not Hatsune Miku, nor any other well-known Vocaloid. In fact, the voices you're hearing are from unique Vocaloids created specifically for this game.
19 (identified): This style MUST remind you of something, no? Go with your gut -- this is indeed from a game in the series you're thinking of.
20 (identified): Kinda creepy, no?