I've actually seen Riviera on shelves during biweekly visits to stores since the game came out, and most of the time you can get the game online for the same retail price if you can't find them locally, or even on the Atlus website. The same was with Trauma Center. Although it did go through several reprints, you could always get them online for about retail price. before the reprints were announced.
And yeah, like you said, with the reprints in effect, their games are even easier to find now.
But anyway, just because a game is rare doesn't mean it's good. I mean, Elf Bowling is considered hard to find.
All games become rare after a couple of years in print anyway. The exception being games that are hits.