Hey, Misty actually came across as being a friend to Ash even in the first season compared to Naru Narusegawa and the Hinata Inn girls towards Naru Narusegawa from Love Hina. At least she didn't beat up Ash just because he happened to be at the wrong place at the wrong time, or heck, just for the heck of it, while Naru and her fellow dorm girls were rather notorious for their horrible treatment of Keitaru Urashima, who didn't deserve the beatdowns at all. Not to mention she risked her life in Episode 4 to save Ash from Samurai when it seemed as though the latter was going to kill him (and she makes absolutely NO reference to her bike at all during that time). If that doesn't speak towards viewing him as a friend and actually treating him like one, I don't know what does.
And personally, that whole trying to get with the ladies and ending up failing horribly gag was simply not funny the first time around, came across as him being a womanizer (I never found those jokes funny, heck, they weren't even appropriate for the age bracket. Didn't like it with Lumiere in Beauty and the Beast or Glenn Quagmire from Family Guy or Charlie Harper from Two and a Half Men, I certainly wouldn't like it with Brock). I tolerated it during Kanto since at least there he also spent his time actually mentoring Ash and also doing stuff that made him overall redeemable like spearheading that rescue of Charmander, stuff that made him more than just someone who skirt-chases, but Johto onward it just made me sick. It was so bad I actually was deeply afraid when Brock returned that they'd make him that yet again. Fortunately, they toned down on that aspect to such an extent that he only did it exactly once in the entire arc, via one of the teachers, and other than that kept a lid on it.
Besides, whether they felt like friends or not ultimately means nothing in the end: What matters is whether they'd actually be useful in terms of the plot. Maybe if Brock when resuming travel explicitly changed his goal to be a Pokémon Doctor, which, let's face it, proves to be a LOT more useful than being a Breeder when he's not even allowed to actually breed his Pokémon, I'd probably welcome his stay or at least tolerate it. As it is, though, Brock in AG and DP definitely had overstayed his welcome as it is. Misty at least had an actual viable goal that if anything would have been greatly expanded upon during AG at the very least.