I do agree that a champion's voice and attitude can affect the fun of the game. For example, Jinx is a ton of fun to listen to, which makes me feel slightly better when playing (Twitch is also amazing, but I don't own him)
Anyway, good on you for playing who you want and expressing yourself. I play a variety of different champions, but I always play who I want to. For example, recently I've been in the mood for aoe playmakers, so I've picked up Viktor and have been playing a lot of (by my standards) Orianna. Sometimes I want to play super tanks or hypercarries... you get the idea. If I don't know who to play and can't decide, then I jump into ranked and play what I get