I have played Assassin's Creed 1 and 2. I would like to skip over Brotherhood and Revelations if possible just to save time and go straight to AC 3. Would skipping those two games leave me lost in AC 3?
As far as the past Assassins' story goes, you won't be lost. Ezio's story is largely unrelated to Connor's except for the main fact that they're both connected through Desmond.
As far as the present-day Assassins' story goes, everything concerning Desmond and his party WILL fly over your head if you miss Brotherhood and Revelations, especially everything related to Juno, Minerva and Tinia.
So if you want to fully understand the WHOLE story, I highly suggest you don't skip the Ezio trilogy. They're not even that expensive on Steam. =p
No you wouldn't be lost. I skipped over one of the expansions (revelations I think) and didn't finish the other, I followed AC3 just fine.
However, there were parts of AC3 (when you play as Desmond instead of Connor) that I found incredibly boring and unenjoyable; perhaps that's related to the fact that I was missing some storyline context from the previous games.