How many games do you need to be interested in before you buy their console?

It could be one. I bought the 3DS just for Professor Layton and the Miracle Mask, since it was a direct sequel to Professor Layton and the Last Specter on the DS and I wanted to see what the full story would be. And even though I didn't know that Miracle Mask would have its own direct sequel, I figured there would have to be a few other good 3DS games, and there have been.

If the DS had had just the first trilogy of Professor Layton games and the second trilogy had started on the 3DS, maybe I wouldn't have bought it, since the first trilogy tied everything up.