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.
