In SS, fly's base power is 90, which is actually pretty good. The only flying attacks that are stronger are sky attack, aeroblast, and brave bird, and I don't consider sky attack "better" because it gives free turns to the opponent.
Aerodactyl, Articuno, Charizard, Crobat, Delibird, Dodrio, Doduo, Dragonite, Farfetch'd, Fearow, Golbat, Ho-Oh, Hoothoot, Lugia, Mew, Moltres, Murkrow, Noctowl, Pidgeot, Pidgeotto, Pidgey, Skarmory, Smeargle, Spearow, Togetic, Xatu, Zapdos, Zubat
/ds4 gen<3,brave bird,all
Crobat, Dodrio, Doduo, Golbat, Ho-Oh, Murkrow, Pidgeot, Pidgeotto, Pidgey, Skarmory, Smeargle, Zubat
So how exactly do "Most of the pokémons that can learn fly also can learn better flying moves"?