ME1 - 60s-70s - Idealistic travels. Classic.
ME2 - 70s-80s - Badass fights. Killing roboids.
ME3 - 80s-90s - Dark warfare. Strange plots (okay, theorizing-me is getting into this, but more clearly just consider Leviathan and Geth Consensus).
MEA - Halo. *cough* I mean 90s-00s. - 'Modern.'
Its a 'new age' for Mass Effect and the gist so far, including even writer hirings, seem to fit that concept to me.
I think Andromeda will be very much about a higher level conflict of cosmic armies, or at least the starting up of it. I think we'll be consistently propelled into a more active movement (including travel, socializing, combat) through the world and it will unveil more alien politics than ever.
A mix of low and high sci fi again. This time the low being the Battlestar Galactica 'ragtag' fleet nature. And the high being the opening to more advanced and intriguing technology in Andromeda. With the 'Tempest', we may find things that make all our dreams come true, though we have a smaller and more isolated galactic force in the meantime.