Aye - Apollo was my introduction to live music. Fab though the stage was ludicrously high and they had glitter on the walls. Remember being up in the balcony and feeling the whole thing moving freakly with everyone stamping their feet. Still freaks me out when that happens.
I love King Tut's and the ABC. Barrowland is fab - but as others have said can be a nightmare getting a drink. Quite like the Hydro but not really a fan of big gigs.