I don´t use legendairies because most of them are just ugly and uninspirered.
The kanto bird trio was a joke to me back in the RGY days...never used a single one..
the jotho beast trio isn´t interesting either..Suicune is okay, but nothing I´d use.
the golems are a bit better,but not much and I don´t like their tank-ish use.
Mewtu is cool, but my team was full at the end of RBY, no space for it.
Ho-oh is..urg...I just don´t like its design ^^; Lugia is better, but in the end, nothing special and couldn´t gain a place in my heart.
Groudon works as a godzilla-like pokemon but I don´t want something that big on my team..I can´t imagine having a pokemon like that. Kyogre is a whale-like pokemon..I´d rather use wailord ( which is too big as well ^^ ), rayquaza isn´t my cup of tea either, and I don´t understand the whole "dragons are so cool"-thing...
Latias and Latios are both pretty cool though..I never trained one, but I must admit, I like them ^^
never had a chance to get an event pokemon, but I´d want them for pokedex purpose only.
I wanted Lukario on my DP team as my very first proberly trained legendairy..and than...he isn´t one ^^;
You see,not all people dislike legendairies because they think they are "too powerful", I just happen to dislike most of them as there are many other pokemon who appeal to me
also, keep in mind that the starters are pretty rare as well, at least ingame as you can only get one of the three starters each game without trading.