It's OU instead of Ubers mainly because of its horendous typing (if I'm correct, Celebi has the worst type combo in the game), as well as lesser stats compared to other Ubers. OU only means that it's a popular choice. Celebi isn't overly abusable and powerful as is the likes of those in Ubers. Rarity has nothing to do with it.
Oh. I thought the tiers were based on usage though...It just seems that if a Pokemon was semi-impossible to get, it couldn't be used enough to be OU.
I'm pretty sure tiers are decided based on usage on Shoddy Battle, though I'm not 100% sure about that.
HGSS make Platinum look like a really bad game, IMO. The entire graphics section looks to be upgraded, and for Pokemon that's very good, seeing as how most pkmn games are 10/10 gameplay but like 4-6/10 graphics...
Wouldn't it be great if they made a Wii game of Pokemon that included the 4 regions(Kanto, Johto, Hoenn and Sinnoh) on one large map, and you could play through 32 gyms and get every pokemon? It could be like a massive remake, and the graphics could be really well done.
