Garchomp is on equal ground with Attack Deoxys, Rayquaza and Groudon. In Attack Deoxys case, it cannot be comparable to Garchomp simply because it has paper-thin defenses whilst Garchomp is comparatively more bulkier, I would feel that Garchomp is better simply because it has more opportunities to switch in.
As for Groudon, Garchomp counters roughly the same stuff as it does and boasts higher speed but comparatively less attack, and a boosted Outrage. As in Rayquaza's case Garchomp outspeeds it initially, while Rayquaza does get Extremespeed on a whole Garchomp does not need a priority move due to its unique speed base. Garchomp functions well in Ubers simply because of its base 102 Speed which would allow it to outspeed a lot of threats in which Ubers are specifically designed to outspeed - this gives it a greater edge, and its speed base allows it to outspeed threats like Palkia and Rayquaza.
Heracross is really slow. It has a great counter in Gliscor as well as Megahorn and Close Combat being an easy switchin for the ubiquitous Gengar and Salamence.
EDIT : KT, Weezing =/
Aerodactyl is a monster in UU having a great speed and the attacking stats and coverage to pull off a sweep - if its counters are below 70% they basically get demolished.