I actually quite enjoyed the elevator rides in ME1. They provided a lot of crucial world-building, and also they replaced the infernal load screens, which I loathe and despise. I also enjoyed the routine of disembarking and boarding the Normandy. I thought it added some realism, and once again, it took the place of a load screen.
Load screens are not only boring, but they are static and break the flow of whatever you're doing, and badly break immersion, so elevator rides would be a welcome return.
As long as they had the same level of polish that I can only assume (and hope) the rest of the game will have, and are more engaging than the somewhat static affairs of ME1. I enjoyed them, but they could have used a little more going on. I liked that you could see the floors whizzing by behind the elevator, but some elevators with some breathtaking vistas behind them would be really awesome. That, and if there's a really extensive pool of dialogue so that it won't repeat for a long time. Also, context sensitive dialogue according to where you are, as well as what's happening now, what's just happened earlier, and what might happen later would all be great as well.
I really enjoyed aspects of ME1's Citadel, as well as ME3's, but none of the games have hit the right balance yet.
What I would like (aside from an open-world Citadel) is one that is bigger than ME1's, but has a floor plan that makes sense, and that includes a variety of areas like what ME1 had, as well as ME3 with the Citadel DLC's areas. That and a return of the elevator rides and the abolishment of loading screens.
Also, as much as I enjoyed the squad banter on the Citadel and hubworlds in ME1 and ME2, I also liked it in ME3 when Shepard went alone. I thought it made more sense in a way. And seeing squadmates going about their own business on the Citadel independent of Shepard added a lot, I thought. It made them seem more like living people with their own lives instead of just characters who did nothing when not with Shepard.
Also, I thought it was great seeing squadmates milling about on the Normandy, leaving their quarters and hanging out in different areas of the ship, and talking to each other instead of only to Shepard, and only when he approached them.
I would like to see even more of both of those things in the future. But I also like having squadmates with me on hubworlds, so what I would like to see is A) a return of the disembarking/boarding process when your ship is docked at a hub, and B ) the ability to choose a single squadmate, or two (or however many are allowed if more than two) OR the choice to go alone.
You could leave your ship and go into the hub with a squadmate or two, or alone, and while there you may see other squadmates doing something on their own or even in pairs or a group.
Imagine, using ME3 as an example, going to the Citadel and you decide to head into Purgatory. You get on an elevator and choose that floor and ride it down, hearing a news report about something that happened a few missions ago while watching out the window and seeing a view of the floors as they pass, or maybe the view of the Presidium. When you step off the elevator and into Purgatory, you look over and happen to see Garrus, James, and Wrex all hanging out a table having a drink together, having a good time. You overhear their conversation and what you hear could be anything. They could be talking about old war stories, or the mission you just went on, or what's next, or they could be talking about anything BUT business. You may be by yourself, or maybe you're with Liara or Tali or whoever. Either way, you could sit down and join the group for a drink if you want, or you could leave them alone to unwind without their CO around.
One of the things that would be great about that is that those characters were there doing something on their own, not just waiting there for you (the player) to interact with them. It makes them seem more lifelike. I think things like that would add a ton of personality and realism.
And going back to elevators and removing the load screens would make the entire experience seamless. From the second you step off your ship onto the hub to the time you return would all be seamless.