I'm pretty sure that the first licensed comic I actually bought would've been a Star Wars comic. I don't really remember ever buying any of them, but I remember always having them around (For some reason, I specifically remember them always being around when I was sick, although I do remember eagerly running home from the newsagent with the first issue of Return Of The Jedi, hoping to find out what happened in the new movie before it came out, and being somewhere between excited and upset to realize that the movie adaptation only filled the first third of the issue, with a random SW story and The Further Adventures of Indiana Jones filling up the rest). The first one I remember actively collecting was the Marvel UK version of Transformers, although I didn't think of that as a licensed comic; my head didn't work that way, yet, so it was just a comic that was connected to those toys that I thought were awesome in some mysterious way.
So why is there some kind of stigma against licensed comics these days?
Part of it could be the whole idea of "selling out," as if there's something less worthwhile about working on a toy comic than, say, Justice League of America, I guess; it's not an argument that really holds water (Creators neither own nor control either type of book, after all), but there's certainly that attitude that exists - Maybe the problem is that it's rare to see top-selling creators at the height of their powers work on licensed comics, beyond the occasional cover? Gone are the days of Walt Simonson and Tom Palmer doing Star Wars (Or, going back further, Simonson and Archie Goodwin doing Alien for Heavy Metal), with very few exceptions. Or, simply, it could be that licensed comics are seen as lesser because they're not the primary medium for the characters, and that kind of thing is important for comic fans (See also: Why comic fans are so suspicious of adaptations of their favorite comics ahead of time)?
(Some commenter has already decided to say that it's because licensed comics suck, but that's not really true; personally, I'd hold recent issues of Buffy, the Star Wars books, Bill Willingham's Angel or especially GI Joe: Cobra up against most Marvel or DC books in terms of quality. I think there are some great licensed comics out there, certainly enough to balance the not-so-great ones.)
I feel like I completely get why publishers like IDW, Dynamite and Dark Horse put out so many licensed books, from a business standpoint: There's an immediate audience there for them, as well as a buy-in to a brand recognition that could help grow the publisher's audience in one fell swoop (or even the comics audience in general - You can't tell me that new readers didn't come into the medium for Buffy's eight season or IDW's upcoming True Blood, which is being sold via HBO's website as you read these very words, bypassing any traditional "New readers won't know where to find them" complaint, for example). And, clearly, they must be selling well enough to continue appearing. I just wish that they didn't always seem like second class comics citizens, is all.