I didn't really mind it, because it was shown to be harmless and someone always dragged him away before it went on too much, especially if the girl was getting a bit creeped out. It was also fairly implicit that Brock would have absolutely no idea what to do with a woman if one agreed to go out with him. However, the running gag did get quite stale over time and by DP it was ridiculously over-the-top. Cilan's relentless taste metaphors and enthusiasm for many things may irk some, but it at least throws some variables into the mix.
I don't know about you, but the one thing that I really hate about Brock is his womanizing shenanigans. That disgusted me beyond belief, almost to the point that I was going to say, "Good Riddance," to him once he left Ash.
I adore them both and think both have their merits and flaws, but as it stands Cilan has more potential than Brock. He's also more likeable to me on a personal level- where I equated Brock to like... my friend's older brother, I think of Cilan more like a friend. Less removed, you know?
Meh. It's not about me, really. It's about the kid. I don't think I'd be a good person to be responsible for another human's development and view of the world. I'd rather just be a babysitter/secondary adult for my nieces and nephews and give them another reference point for adult life/philosophy.