Don't you think it's somewhat extreme to categorize Ticket to Ride together with 18xx and the Steam series? TTR is effectively just a set collection game, and one of the most prominent gateway games, as opposed to the other mechanical beasts that only has somewhat of a thematic similarity.
I didn't, but that's because of how I was introduced to them, via "Railways of England and Wales" (or something like that), which is basically an alternate map of Ticket To Ride and (according to the aficionados) supposedly a lot better due to having a smaller map. I remember very clearly that the introduction began by asking if I liked "train games", to which I had to answer that I didn't know. five hours later, I had a sneaking suspicion the answer might be "no."
Which is part of the reason for my preface: I don't like that style of game (brought to me as "train games"), but I know some people do. It's clearly not for everyone, and having experienced it, I think I can explain why it wasn't for me and might not be for 'you'.
@ Munchkin: That's the weirdest thing -- since one of my friends (whose family had a MASSIVE game cabinet) owned it, the same group of us would occasionally forget just how badly the last round went and a month or more later bust it out. We were all RPG gamers, we knew the joke, and the individual cards are hilarious. Yet, somehow, the game ended at A) or B) every time, even with that core group. We'd avoid it for a while, but eventually time would wear away the pain, or a friend who didn't so commonly come to game night would ask what it was (Failure C sometimes resulting: at least one person who left game night over Munchkin never returned to my knowledge)... My experience may not have been scientifically rigorous, but it WAS more than a single event.