Aside from the ending, I find it funny how during the entire duration of the game Earth is under attack. So when you're busy doing side missions or romancing Liara/Ashley/Miranda/etc. or just lounging around, Earth is being destroyed. Earth is sure a lot more resilient than the other planets that fell to the reapers.
I think the most emotional part of my first playthrough was what happened to Tali because I didn't have enough points to make some other choices.