Terminal 1 (Southwest - US Airways): Two story ticketing area, rest is non-descript and crowded. Baggage claim has bus station feel to it.
Terminal 2 (Northwest, main tenant, and a hodgepodge of other airlines): Last terminal building added to LAX. Dates back to the 80's. Originally constructed for Pan Am. Ticketing area is one story, very cramped and poorly lit. Redeemed partly by a monumental and modern look to security checkpoint, but gate area is rather ordinary. Worst thing is that secure corridors for arriving international passengers block one from getting an unobstructed view of runway outside. Baggage claim has bus station feel to it.
Terminal 3 [American (intra-California and intra-West) and Alaska, main tenants]: Best example of what the original terminals must have looked like at LAX. Quite dated. Former TWA terminal. Since taking it over, AA has claimed much of the gate space and other facilities. AA has tried to spruce up the gates with its own signage and colors. Still, many parts of the interior have a worn and dated appearance. Ticketing area is one story, cramped and poorly lit. Baggage claim has bus station feel to it.
Terminal 4 [American International and Long-haul]: The cream of the crop of LAX terminals. Renovation completed early this year. AA changed almost the whole structure of the original building - adding a vaulted two-story ticketing area, a second story over the first departure hall for an Admiral's Club with high, angled glass walls, very contemporary palette of colors, indirect lighting, and a terrazzo floor with a very intricate pattern in red and blue. Artwork, alone, on floor and walls of security checkpoint cost $800,000. Don't miss it when you are there. Oh, I almost forgot. There are floor to ceiling windows ringing the walls of the second departure hall. Perfect vantage point for spotting.
Terminal 5 (Delta, main tenant): Renovated in the 80's. One story ticketing area, poorly lit. Monumental entrance hall serving no real purpose. Too much beige in the color palette. Gate areas are well laid out and interspersed in a café style with concessions - best feature of terminal. Large palms planted inside the terminal reinforce the appearance of an outdoor cafe. Retains one feature of original terminal, the rotunda separating the two gate areas - somewhat inconsistent with rest of architecture. Despite that, probably the second best terminal at LAX.
Terminal 6 [Continental, United (International), others]: One story ticketing area. Continental's gates have new signage and carpeting and some distinctive space planning and decoration. Widebody gates, however, that Continental shares with United are abysmal - ratty carpet, windows with the solar film wearing away, and formica podiums at the gates. Baggage claim has bus station feel to it.
Terminal 7 and 8 (United): A hodgepodge of buildings. United has added to the terminal and renovated parts of it several times, most recently in the late 90's. I think they spent about $300 million dollars the last time. Hard to see where the money went. Last renovation hardly touched the form of the ticketing area, rotunda, and southernmost departure hall. Too many things wrong with this terminal for an easy summary. Worst part of it has to be the southernmost departure hall which as a result of a previous addition provides hardly any view of the runways. Lighting is extremely poor. In most places, United simply painted over the metal wall panels that were part of the original structure of the departure halls. Palette is a bland blue, white and grey throughout. The Terrazzo floors are mostly white with a line of red squares here and there. Compared to AA's floor, United's floor is a real embarrassment. Given all the mess they created during the last renovation, in the end it was much ado about nothing.
I left out the Tom Bradley International terminal. I'll just simply say that on my list of terminals it would rank 3rd - with AA's Terminal 4 being No. 1 and Delta's terminal 5 No. 2.