Imo, the show went downhill during the second season, with Brock gone and all. Then they started adding new monsters... I can understand keeping the game/show fresh by adding new things, but a lot of the new monsters are ridiculous. The games are still fun, though I don't have a DS (or Diamond/Pearl).
Oh, and why is it that legendaries like Mew and Celebi are available in the Japanese editions, but for the US editions you either have to go to a Nintendo event or use a (potentially harmful) cheating device? What's the point of that???