Get them all besides 11. It's a MMORPG and therefore rather different from the rest. And you'll have to pay a monthly fare to play it online, too. 4 and 6 are a must (6 especially). Don't forget to buy 9 as well, it's really fun, probably more than 8 in my opinion. Oh, and 3 is sweet. I suggest that you get the Nintendo DS version, unless you want a real "original" feeling, in which case your only option is a Famicon emulator.