Why doesn't Daggerfall or Arena get brought up in these threads?
People don't play them, despite their being free for 6 years, in Arena's case, and over a year, in Daggerfall's case. If people supposedly hated Oblivion's fast-travel and setting, however, they probably wouldn't care. Basically, this isn't an Elder Scrolls fan forum, it's a Morrowind fan forum with some Oblivion fans sprinkled in. Both have members that don't care at all about the series and/or just a want a sequel to their preferred game, hence we have threads like these which typically lean towards Morrowind because the majority of the forum members, here, started with Morrowind and Oblivion gets thrown in because some people started with Oblivion, instead (start a "Which Elder Scrolls game did you start with and which is your favorite?" thread with a poll and take a look at the correlating results). Arena and Daggerfall are never included because, as I said, this isn't really an Elder Scrolls fan forum, at many times. People don't understand the change that constantly occurs within the series, they don't know much of anything related to the older games (Cyrodiil started off as a forest, fast-travel came from older Elder Scrolls games, and "generic fantasy" settings are standard for the series... as are competitions involving fans of an older game and fans of a newer game, usually with the fans of the older game initiating the attack on the newer game), and people don't seem to even notice their existence, at times. I could swear some people see the "III" in TES III as a "I" and the "IV" in TES IV as a "II", and sometimes as a "I". The tradition will likely continue and, depending on how long the series continues for, Morrowind and Oblivion may also join the ranks of the untouchables of the Elder Scrolls universe.
Well, that's my theory, anyway.