I loved the amount of games and the variety. It was cool to walk into a new arcade and more or less instantly know all the games and where they were simply from the sound effects. I bought those Arcade Ambiance CDs just to relive that feeling from time to time. Unlike some here I don't think that home consoles ever caught up to arcade cabinets. Yes, in terms of CPU speed and raster displays but no home unit, except maybe the Vectrex, has ever equaled the vector displays from the classic arcade games, and no console has the array of controllers (with their custom layouts) that arcade games had as a whole. I miss that the most, I think.
I love the side art for the games (those games where you could see their sides, at least) and the dimly-lit rooms the games were in. As someone else mentioned, the blast from sunlight when I left was cool in a painful way (you can do that now if you spend all night in a 24-hour strip club in Vegas, haahahaa). The scene in "Tron" at Flynn's is a fantastic representation of the overall arcade vibe. I agree that once arcade games became nothing but 1st-person shooter games and 1st-person racing games I stopped giving a shit. I liked that nervous feeling you could get when trying a new game, others watching you to see if you sucked or not. It was fun, sometimes, to just watch a real pro go at a game and kick its ass, too, it was like nerd ballet.
The worst thing that happened to arcade games, from my point of view, was that the resolution got a little better. When games were 8-bit based you had to fill in a lot of blanks for what the game claimed you were looking at (vectors most of all). The ships, the enemies, the locations, they were all approximations, very abstract. I think Xevious was probably the best of the "worst" looking of the era in terms of detail. But after that, games got more detailed sprites and graphics. But they were still far far away from today's "photoreal" games. Yet they were detailed enough for you to notice how bad the representations were. Meaning now the crudely-shaded and shadowed ships and enemies were no longer abstractions but instead really shitty versions of the actual things they claimed to be. That turned me off completely. I guess I'm biased because I was around for when Space Invaders and Galaxian were new but I always preferred the LEGO block designs of early sprites and ships and enemies (and vector wireframe versions). But looking at something try to look real, and really failing at it (a lot of those Mortal Kombat style side-view fighting games), that was miserable to me, particularly when the game was trying to represent people. Spaceships and vehicles were more tolerable at that resolution and detail. But games makers started focusing on the visuals (how realistic they could make the various elements) and not the gameplay.
Lots of games in the late '80s and beyond devolved down to 1 joystick and 2 buttons, very boring and repetitive. My favorite games usually had odd control set-ups (Tempest, Star Trek: SOS, Centipede, Lunar Lander, etc.) so that was something I remember fondly as well.