That is most likely because SR3 is when the series took a turn from serious and funny to all out fucked up funny.
Saints Row one had the classic style GTA character who doesn't talk. You actually spoke on 4 or 5 occasions only, once upon the victory of each gang (3 gangs) and once (twice maybe, can't remember for sure) upon winning the game. Each time you have a high pitched weird ass voice. In SR2 you got way more customization and your character started speaking. You could pick your voice, those choices were available in the next two in the series as well, but with more customization. But in SR2, while the game was still very funny, after being betrayed by your allies in the first one, you set out with a more serious tone to rebuild the gang which had since fallen apart while you were in a coma. In SR2 you're now the boss of the Saints and have to re-take Stilwater, for good this time. They thought you were "hard" in the first one, but in SR2 you're the ultimate badass with no mercy.
My personal opinion, I love the shit out of all of them, It's hard to pick a favorite, impossible really. I thought each time a new one came out that they just got better and better, but there are things that got lost along the way too. So, while I still believe that, it's easy to note things that were awesome in all of them that can't be a part of a newer one without taking away from what makes the new one good in a different way. If you understand my meaning.
Favorite weapon so far, 420?
Mine is definitely the Dubstep gun, although the 'Merica gun is also very badass. I actually received a physical toy copy of the Dubstep gun, it lights up on one side and has a laser point while the trigger is held, playing the dubstep song heard in game when using it.
