Legendary was never meant to be related to strength. That's what uber is for. Legendaries were suppose to be just really rare Pokemon. I mean out of the first five legendaries, which made the original definition of 'legendary Pokemon'. Most of them are part of a trio.
But which Pokemon are legendary and which ones aren't has never been that official or definitive. Bulbapedia, whom try to document which ones are and aren't, have had a lot of trouble with the subject. For example:
Rotom was listed as a 'legendary Pokemon' in an official handbook. In fact nothing official has ever disproved that it indeed is. Some people say it is, but it generally isn't considered legendary, because most people disagree. When not considered a legendary, it is:
- The last non-legendary in National Pokedex order.
- The only non-legendary to have legendary battle music playing during its battle.
- The only non-legendary to have an event item associated with it.
- The only non-legendary to change stats when it changes forms.
- The only non-legendary to be banned in official Pokemon tournaments (it's other forms, not its basic form).
etc.
Note 'Legendary Pokemon' written under 'Plasma Pokemon'.
Unown is clearly legendary in the anime (appearing in legendary Pokemon books and being explicitly stated to be by Prof. Oak), but not considered one by most people. Phione was confirmed by Nintendo (when they were asked) that it was non-legendary. A while later they said it was.
Dragonite was placed in-between the legendary bird trio and Mewtwo and Mew, in National Pokedex order. Arcanine is stated as a 'legendary Pokemon'. Lucario is hinted at being legendary in various canons. Ninetails is a legendary Pokemon in the PMD1 canon.
And various other Pokemon have been related to legends too.
But which Pokemon are legendary and which ones aren't has never been that official or definitive. Bulbapedia, whom try to document which ones are and aren't, have had a lot of trouble with the subject. For example:
Rotom was listed as a 'legendary Pokemon' in an official handbook. In fact nothing official has ever disproved that it indeed is. Some people say it is, but it generally isn't considered legendary, because most people disagree. When not considered a legendary, it is:
- The last non-legendary in National Pokedex order.
- The only non-legendary to have legendary battle music playing during its battle.
- The only non-legendary to have an event item associated with it.
- The only non-legendary to change stats when it changes forms.
- The only non-legendary to be banned in official Pokemon tournaments (it's other forms, not its basic form).
etc.
Spoiler:
![[PokeCommunity.com] Legendaries = Big Thumbs Down. Your Views Please! [PokeCommunity.com] Legendaries = Big Thumbs Down. Your Views Please!](https://archives.bulbagarden.net/media/upload/thumb/9/9d/LegendaryRotom.jpg/500px-LegendaryRotom.jpg)
Note 'Legendary Pokemon' written under 'Plasma Pokemon'.
Unown is clearly legendary in the anime (appearing in legendary Pokemon books and being explicitly stated to be by Prof. Oak), but not considered one by most people. Phione was confirmed by Nintendo (when they were asked) that it was non-legendary. A while later they said it was.
Dragonite was placed in-between the legendary bird trio and Mewtwo and Mew, in National Pokedex order. Arcanine is stated as a 'legendary Pokemon'. Lucario is hinted at being legendary in various canons. Ninetails is a legendary Pokemon in the PMD1 canon.
And various other Pokemon have been related to legends too.