The Crowne Plaza is really nice, right next to the Albert Dock, Beatles Story, Tate Liverpool etc, about a ten / fifteen minute walk into town. Crowne Plaza Liverpool 0151 243 8000
If you want to go upmarket Liverpool has just opened a Malmaison, 0151 229 5000. Don't know about prices though I would have thought it would be very expensive.
Marriott is quite nice but is right next to the bus gyratory so can get a bit hairy at night time! 0151 476 8000. Also I don't know what parking is like there.
Whatever you do don't go to the Adelphi!!!