Looking back from Kanto to Unova we’ve seen stalking in many forms; from a crush or admiration, desire to steal or kidnap and other reasons. From TR trying to steal Pikachu, Pokemon that follow Ash and the group around for one reason or another “stalking” in the Pokemon world is more than simply looking at someone profile page and looking at all of their pictures.
Like Helga from Hey Arnold, Bulk and Skull from Power Rangers and many other series, we see characters that follow the main character in elaborate disguises and hiding places.
Now to get to the point we know Brock can tell every Jenny and Joy from each other (aside from their own relatives). The famous marker-drawing Jigglypuff following the gang all the way up til Johto (and the Jigglypuff from that one Hoenn episode that could be the same one). The rich ladies Snubull that followed TR around because it loved to bite Meowth’s tail.
I would give my vote to Brock, the poor guy literally falls for anything female that moves (reminds me of Oshawott in the BW series...wonder if his fall for any girl Pokemon at first sight is a way of sneaking the "Brock character" back into the series, ah something to think about there haha).
Looking at the Hoenn league for example; Max used his Pokenav to look up data on the league's rankings and competitors Pokemon and strategies ok that's legit considering it was to help Ash, but Brock had a book not to write down battle stats but all of the females. While that seems "sort of" harmless he mentioned that he listed the name, location, interests, etc of those girls! Creeper...
But the #1 reason I think he deserves top stalker is because like I mentioned before he could tell any Officer Jenny or Nurse Joy apart from the others, I was impressed yet creeped out back in the Kanto episode "Round One Begin!" when he could tell them apart haha but it was kind of funny.
TR does stalk the gang for Pikachu, but as seen in numerous episodes there are a lot of times when they come across the "twerps" by pure luck but they have been seen sneaking in bushes or looking through their submarine lens for them. So, I'd rank them at a solid #2.
Of course there are many others but who do you think tops the list for “best/top” stalker in the Pokemon series?