Well, the Advance Gen's gymleaders were pretty forgettable, but I can tell you Steven's star pokemon is Metagross and Wallace's is Milotic. And Tate and Liza are the Solrock and Lunatone kids. And how can you forget Byron and his
BASTODION! (Granted, Volkner's Luxray, Fantina's Driftblim are probably more memorable.)
Pokemon games have always been easy if you grind enough and use elements to your advantage.
And people complaining about not being able to use the pokemon you like: Well, that's your choice. No one is forcing you to you strong pokemon, especially ingame. As for game mechanics, for some people, ignorance is bliss but not for me.
For something else I miss, it's the more cohesive pokemon designs. The first 150 pokemon usually shared physical features that made it feel like they belonged in the same group. I like a lot of pokemon in the later gens, but c'mon; Spiritomb just looks weird.