id managed to avoid any big spoilers and had even refused to watch the main trailers (just the watched the teaser)
on the day i remember being incredibly excited - comparable to excitment levels for Star Wars I, Matrix 2, Superman Returns, Indy 4, Star Trek 2009...(but maybe even more so as this was Ridley Scott returning to Alien again! his 3rd SF film! his first for 30 years since BR!)
the opening with the engineer was tremendous and eerie and stunning and had an epic 'Wonders of the Universe' style vibe (it actually felt like you were watching something that took place millions of years ago )
but it wasnt until the opening scene of David on the Prometheus that it hit home and i was like 'oh man oh man this is crazy im watching Ridley Scotts Alien 5!....Ridley Scott directing a new Alien!!'
following him around on board what just looked like an advanced Nostromo (There was even a sort of Resurrection nod with the basketball) ....the last time id seen anything like that was Danny Boyles Sunshine but that wasnt an Alien film. i recalled reading something about either Scott or Cameron saying they often wondered what Ash or Bishop got up to while the crew slept - and here it was!
For the first 20 or so minutes i kept thinking back to the lost Cameron/Scott Alien 5 that was nixed in favour of AvP and realised i was pretty much watching it now in 2012! (sans Cameron of course) f**k you AvP!!
it was a similar feeling to watching Phantom Menace for the first time in the cinema - the huge yellow Star Wars logo then seeing 'Episode I' crawl past (not IV, V or VI as usual) or seeing Indy 4 and the Paramount logo/opening credits..but all the more intense as im a bigger Alien fan than SW/Indy