Quoted By:
Sinnoh>Johto>Kanto>Unova>Hoenn>Kalos
Sinnoh has Flint, who I think is the first E4 you actually meet outside of the E4 for the first time in the main game. Johto has Karen, the first Dark League member, Bruno and Koga who make a comeback from a previous. Only Will is the really forgettable one. Kanto has Lance and Bruno again, who go on to do some shit/return, but Agatha and Lorelei are really dull. Unova E4 actually get some stuff done in earlier/later games, and IIRC, Marshall actually does some things in BW2(which I never played). Also get points for being the first E4 you can fight in any order, none of them are the "strongest" member. Hoenn just feels kind of like a repeat of older rosters, and Kalos is just completely and utterly forgettable aside from Drasna, who's only memorable for third part coom material.
Haven't mentioned Champions at all besides Lance, but all of them are honestly great besides Diantha, who I just think is completely and utterly drool.