Technically CB Dragonite IS boosted (as Choice Band makes Dnites Attack become 604). While CB luke can't compare to CB Nite, Dnite has an arguably worse typing. Most of the resists Dnite has, Lucario also has (bar the water and fire ones). But in exchange for neutrality to water and weak to fire and fighting, Lucario has Dragon, steel, and dark resists. Dragon and Steel IMO, are much more defining types in the metagame, with Latios and Scizor running amok. And Lucario can kill both of these with the appropriate move. With everything running Mamoswine/Weavile/*insert Ice Shard user* to check dragons and Lando-I, Lucario's resists allow him to set up on nearly every single one (and just KOs Mamoswine with CC/Bullet Punch). All of them fear Bullet Punch/CC to the face. Plus, Dragnite just isn't as good in the metagame anymore. In BW1, it was an excellent pokemon, IMO underrated, as it had so many sets. But in BW2, its slow, and common scarfers resist Espeed.Those common scarfers are scared of Bullet Punch (cough Terrakion) and Lucario just blows them apart. Also bulkier threats have come along (cough Garchy, 88 HP Lando-I and Keldy) and can take banded Espeeds with relative ease and KO back with the appropriate moves. Is Dragonite a great pokemon? YES Is it a good user of Espeed? YES. However is it a better use of Espeed than Lucario? No. Lucario can bypass scarf mons with other priority moves (Bullet Punch, and NP variants can run Vacuum Wave), Dragonite can't because its too slow, and its other notable priority, Aqua Jet, is weak without rain support. Plus, it Aqua Jet lacks STAB on Dnite. Lucario can switch in many times, because it 4x resists Rocks (which are ubiquitous). Dnite is weak to it, so it can only switch in 4 times before its dead. While Lucario is weak to Spikes, that is far less common.