19th Hint -
It's the first title in the series and is belongs to the latter trilogy.

#20 - Wild ARMs 3 (PS2)

Now we're into the top 20 I'm going to put a little more effort into my game presentations.  So here, at #20, as guessed by Mr. Khan, is Wild ARMs 3.

As I mentioned before, Wild ARMs came into my life at a time when I was disheartened with Final Fantasy, and this was the very game that introduced me to the series.  I found it in a bargain bin in HMV; was looking for a substitute JRPG and decided to pick it up.  Boy, what a ride it was.

Wild ARMs 3 features traditional JRPG combat; a huge world map to explore; incredibly enjoyable dungeons with fun puzzles; interesting, diverse and loveable characters.  All the things I felt FFX lacked.  Mix in a fantastically crazy plot that ramps up significantly as the game goes on, an incredible 'western' motif featuring gunfights on horseback, desolate wastelands and small port towns, and you've just got a masterpiece.  If you haven't played this game yet, now is the time.

Clue for my #19 - Hearing snowmen scream "I'm melting!" as you torch them with a flamethrower has never been such fun.

#20 - Rome: Total War. Even the name is epic. This game is without a doubt, the best tactical strategy game ever made. The scale of it's battles were never before seen. Of course, newer entries like Medieval II: Total War and Empire: Total War have bested this, but Rome was the first to give such an impact. Still, this entry could also count for those two games. Rome however, is situated during the most interesting period for a game like this, in my humble opinion at least. The game's huge map features many different factions, all very unique with a sheer endless amount of possible units and upgrades. Rome polishes itself with the rivaling Roman families arc, which always keeps the player on his toes when dealing with your friendly Roman allies and with the watchful eyes of the Senate.

#19 - ?
This puzzle game can be rolled to all sides!

I missed a day so here's the next two:

21. Legend of Zelda: Link's Awakening (GB, also on GB Color & DS as DX)

This is the only Zelda game on my list. I'm still playing through OoT on VC, never completed A Link to the Past (which I really enjoyed) and Twilight Princess just missed out. However, there's something to be said about the first time you play a Zelda game and this was my first. Maybe it was because I played it as a kid, or maybe it was because it was the first Zelda game I'd played, but this fuelled my imagination in ways most modern games don't even come close to realising. The fact that they managed to cram so much brilliant content into a game boy game was an astounding feat on its own. The charming 2D sprites coupled with the superb design of items, carefully crafted dungeons and clever game progression made this one of the greatest game's ever made. I pretty much played this and nothing else for a 1.5 years; it's just a joy to play.

20. Portal (PC, also on PS3 & 360)

This was pure genius. Only a few hours long with a few bonus maps, but everything was sheer brilliance. The innovative portal gun, some inventive, mind bending physics puzzles and a wonderfully funny script. I played this on my own and went through the whole thing in a single sitting. A few weeks later I spent a few hours of a gaming session with some mates going through the campaign and simply laughing at their reactions. Pure gaming genius.

Clue for 19: This game was a turning point for the series. The first level features a Captain saving his soap from a sinking ship.

Edit: meant to say Marble Madness: Kororinpa

20. Advance Wars (2001)

Dropping from 15th over the last couple years, is the game that actually prompted me to get a GBA. This was pretty much the classic war-type board game brought into the video game world.  In other ways it was so much better.  The results of individual fights were usually pretty predictable so you could strategically plan multiple moves ahead without needing to have too many contingency plans.  The gameplay is fairly simplistic, build, move, attack, capture and there's often multiple ways to win.  Add in a campaign which  ramps the difficulty almost perfectly and its hard to get too discouraged playing this game.  The CO powers give you an advantage for a short time so you have to be careful when you use them and your COs base specialty actually has an impact on what units you build.  Fog of war and varying victory conditions added almost as much extra gameplay as the large set of maps already built into the campaign and war room.  Overall this game shines because it really feels like you can do well no matter who your CO is and the balance of the individual units on top of that works nicely.

19. Sonic the Hedgehog (Mega Drive)

I've always been a Nintendo guy at heart, and the Nintendo v Sega/Mario v Sonic arguments of old always saw me favour Nintendo and Mario, but that didn't mean I dismissed Sega or Sonic outright, unlike others who considered Sega to be their nemesis. I played Sonic games a lot, and in my eyes the first one is the best. The Green Hill Zone, Act 1 is one of the most iconic levels in video game history, and I believe that it is there where Sonic is at its best. Sure later levels in this game and in others may have been more complex, but there's something about speeding through that one level that makes it stand out above all the others.

Number 18 was a Retro revival.

Correct. Perhaps a little too obvious...