Sunset strip pretty much spoiled me for everything else.
That said, what I'd really love in a hub is a tram system populated by other characters, like taking mass transit in a space station and there are other characters you can encounter, as well as having news broadcasts.
ME1 had little to no real life about it, and the weird architecture didn't help. Liara's comments on "prothean" architecture only made it a little worse. I don't think I need to explain all the problems with ME2's wards. It's just so enclosed and confining. It had fun stuff in it, but the feel of the design was just not good to me. I'm not really sure why ME3's Citadel is considered to be so much worse than either of these, because ME1 is certainly expansive, but it's no less awkward and sterile, but ME3's atmosphere was more active. Where ME3 really dropped the ball is the flimsy encounters, and eavesdrop sidequests.
I liked the scope, the expanse - it emphasized just how BIG the Citadel is, that there WAS all that empty space. Compare to the Normandy, where half the squad is crammed into the cargo bay because they don't have their own unique spaces carved out. Here on the Citadel, there's all this ROOM, with the crowd characters moving around casually, not seeming rushed or packed in. The life was in the crowded areas, sure, but the fact that, after the Normandy and Eden Prime, which was full of cookie-cutter prefabs with no individuality or life to them because they're temporary structures, the Citadel really allowed the utter scope of things to come into focus - someone BUILT the Citadel, and built it large enough that there could be all of this space filled with nothing.
Overall, that's one of the things I loved about ME1 that the later games didn't have - that scope, that showing of just how BIG these places are, because there's room for all of the lifeless nothing. Space is big. Immeasurably big. And a lot of that is filled with nothing, at least as far as what we know to be there. ME1 gave that, by having the planet explorations with a whole bunch of nothing, and the Citadel being emphasized as being as big as it is, while still having all of this empty space.