You don't have to be a FGC guy to know T4 gameplay wise was a step back. It did some nice things like non infinite stages and a pretty unique Jin skillset, but it took steps back making those stages completely unelevated, as well as easy to take advantage of when backed into a corner.
Even worse still they took out the second block and replaced it with some lame "switch places" grapple thing that doesn't even make sense.
(i was mostly pissed because they took out a lot of xiaoyu's moves from T3, even though T5 added them back in with the moves they added from T4 which was nice)
In terms of non gameplay stuff, i thought it was pretty cool, since it actually tried to make the storyline of the games actually matter somewhat, and the more serious feel was great, along with the major revision to both costume and design wise to many of the characters. It really felt like a step up thematically.
T5 and T6 and T7 by comparison are all too samey in that department from what i've seen