since Devin Townsend is already brought up — was never a fan of "Let It Roll" opening Synchestra when "Hypergeek" actually starts with the same feel. if he'd worked the vocal (which, i'd argue, is the reason "Let It Roll" even exists) into "Hypergeek" i think the album would work better. Dev historically is fantastic at picking openers (even "Olives!"); maybe it's just the way he wanted Synchestra stated that i'm not into, rather than the song itself.
Meshuggah — "Concatenation" is much better in slower form on Rare Trax, and "Combustion" just doesn't grab me whatsoever.
Iron Maiden — also gonna back The Number of the Beast for this. i was taken aback severely when i realized the title track opens the second side, rather than the whole record! i've never heard a more obvious choice. (maybe that's why they didn't!)
Radiohead, perhaps controversially; i just find "Airbag" and "Everything in Its Right Place" don't quite live up to the rest of their albums. i probably would have opened Kid A with "The National Anthem."
Blackfield — decent song, but "Once" doesn't really pump me up for BFII.
Rammstein — while the record is full of great songs, "Sehnsucht" just doesn't make a great opener.
Tool — "Intolerance" just feels so middle-of-the-record to me. kinda feel like it would have been a statement with more impact to open with "Flood" (and end with "Bottom"), but that kind of talk doesn't go over very well with the fanbase
DT — not a fan of "6:00" (heresy! burn him!), and i side with MP on opening I&W with "Metropolis."
and now for a weird injection of recent commercial radio material:
Deftones — they just can't open their album White Pony very well, whether it's with the usual opener "Feiticeira" (just a boring, offpitch song that doesn't live up to the rest of the album) or the secondary inclusion of "Back to School," which was an awful record company decision anyway.