OkashiiNaito said: Isn't being overpowered the entire point of being Legendary? (aside from being hard to catch and 'unique')
There's a weird, unspoken distinction between Pokemon which are simply "unique" like the trios and Regigigas, and true, world-shattering Legendary ones like Ho-Oh, Rayquaza, and their ilk.
In all fairness though, Regigigas is the one who pulled around continents with ropes, and he's the one who crafted the regi trio, so it makes sense he's tired after all that.