A big underestimation is Gran Turismo. Dragon Quest is another huge one (for some reason people think Final Fantasy is more important, despite not being nearly as popular on the Japanese Market).  The last Final Fantasy sold uner 2.4 million in the Japanese market, and the spinoffs haven't been doing as well as expected.  In comparison the last Dragon Quest sold 3.6 million on the Japanese market, and was an increase of every previous game.

The most underestimated game is (drum roll please)
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POKEMON. That's right, for some reason people like to ignore the second best selling franchise in gaming history. If they ever made a Pokemon MMORPG Blizzard would be kicked on it's ass faster than it could blink. The sales pokemon games get are insane.

Hell, a pokemon mmo would pretty much kill the mmo genre, unless it was done wrong, which is inst possible because all you have to do is take the game boy games and make them online...

Naznatips... What are you talking about? FF12 sold quite well. It did 2.3 million sell-through in Japan alone, and VGC lists its WW shipments just below 5 million, and better than any Dragon Quest game in history.

There's another misconception. That just because DQ is bigger in Japan, that its more important WW. No DQ game has ever reached 5 million sales; FF12 will become the 6th FF game to do so.

dear god, is that a fabio from wizards and warriors Ironsword for the NES?

Depends on the argument, if you dont care don;t buy it, but if you are argui ng what will sell more that kind of depends on the system. 

Sorry I was talking about the Japanese market, and it didn't do nearly as well there as it should, actually selling about the same amount of copies as FFX-2. The FF market is on a huge decline in Japan, if you notice ever since VII sales have been on a steady decline, resting at the current number. The trend shows a signifficantly decreased interest in it.  In America FF is almost as important as it ever was, though again very sad that FFXII will sell less than FFX-2. I'm not bashing it as a game, it's one of my favorite FF games (VI, IV, IX, XII are my top 4), but the FF series is in a sales decline.

FF12 will still be a WW 5-million seller, a mark that DQ is yet to reach. And FF has hit that mark with three games each of the last two generations, a period where only two DQ games have been released. Obviously, FF is still far more important.

That may change soon, as I expect DQ9 to match FF13 in sales, but as of the last 10 years, FF is a waaay bigger franchise WW.

While I largely agree, Erik Aston, there is an important note to make. Final Fantasy sells extremely well in all regions. If a game sells less well than Final Fantasy, it's usually because it's trounced by the franchise in all three regions: Crash Bandicoot Wrath of Cortex, for example, sold well in all three regions (approximately 240,000 copies in Japan, 1.95 in America and 2.78 in Europe), but not as well as Final Fantasy in any of them, and thus was soundly beaten in sales.

Dragon Quest is different. It's beaten by Final Fantasy because of America and Europe: it routinely and consistently sells better than Final Fantasy does in Japan. Looking here:

http://vgchartz.com/worldtotals.php?name=&console=PS2&publisher=&sort=Japan

You can see that Dragon Quest VIII wasn't just a good seller in Japan, it was the best sellling game on the PS2 in Japan. Ever. That says a lot, and it has consequences. Crash Bandicoot is -- at best --  a minor system selling game in all regions; in contrast, Dragon Quest is meaningless in America and Europe, but almost certainly the most decisive game for console dominance in Japan. Over any other franchise, period. That's an important distinction to note.

Just for emphasis, I thought I'd pull these charts up. Here, again, are the best selling games in Japan for the PS2:

http://vgchartz.com/worldtotals.php?name=&console=PS2&publisher=&sort=Japan

Now, for the PS1:

http://vgchartz.com/worldtotals.php?name=&console=PS&publisher=&sort=Japan

Now, for the SNES:

http://vgchartz.com/worldtotals.php?name=&console=SNES&publisher=&sort=Japan

Now, for the NES:

http://vgchartz.com/worldtotals.php?name=&console=NES&publisher=&sort=Japan

In Japan, exactly four games have ever sold better than Dragon Quest on their respective systems: Super Mario Bros, Super Mario Bros 3, Super Mario World, and Super Mario Kart. That's it. In history. It's really hard to over emphasize just how big a deal Dragon Quest is in Japan.

So. Most games that sell 2-5 million copies are medium-tier, moderately important titles that sell a lot of copies, but aren't flagship titles anywhere. They rarely are the "killer app" system sellers we're talking about. Dragon Quest is different: it's a total blank page in Europe/America, but it is the killer App in Japan.

Arguing that Dragon Quest isn't a crucial system seller is very much like arguing that Grand Theft Auto isn't. It doesn't even crack the top 40 games on the PS2 in Japan (any incarnation), but it clearly is a big deal because it sells so well here and in Europe and decides what system a great deal of people buy in those regions.

One of the reasons most people "pick" a favorite console is, quite frankly, they don't have the money to buy a 360, a PS3, and a Wii. Some people do, but alot of people would rather just buy one system (possibly 2) and be happy, without worrying about games they miss.

Like, for instance, I've never played Devil May Cry. And I play GTA on my computer, so no need to buy console versions. I've never played a PS3 aside from the basketball and racing game on demo at Wal-marts and Targets. Will I ever play Resistance: Fall of Man? Who knows? I've heard Gears of War was really good, but will I ever own it? Who knows? Am I really missing out, if I don't KNOW that I'm missing out?

Actually, the people who claim to own multiple consoles can be the worst. Having more than one system suddenly makes them experts and they think it gives them free reign to completely trash one system and put another on a pedestal.