Meh, if you've beat one, you've beat 'em all. They get slightly more advanced each time, but the same plot, with new Pokemon. Which is why I have no problem cheating on any of them (provided I beat it fairly first).
I know some people plan to literally catch 'em all, but I, for one, am not one of them. I catch as many as I can, do as much of the game as I can and usually it turns out pretty freakin' well. I basically end up with any Pokemon that is available in that game (and the other ones you normally can't get in that game), so it's all the same to me.
It's still good to occupy time, but honestly, not my fave selection of game series. And I'm guessing if I actually paid for them I'd be even more disappointed.
“…Judge not what a man has done, but judge what he could have done if he was a different bloke altogether. For art thou a leper? And a leper can changeth his spots…” --Rudy Wade, Misfits (Series 4, Episode 8)