There's kinda already a thread about that trailer.

Though arguably trailers, I have to agree with you about Another Side/Another Story and Deep Dive. Never have I been so intrigued, so riddled with questions that I couldn't wait to have answered, than I did when I saw those, even if the answers that ended up coming to fruition weren't necessarily satisfying.

I also really liked the "Take Back Earth" trailer for Mass Effect 3.