Personally I believe that upon given the choice, yes Shepard should die. Because while he/she has saved the galaxy almost singlehanded up till this point, he/she are only a single person compared to the vastness of a entire universe.
If believe that if Shepard dies (Which would be cool to carry over in a future Mass Effect installment outside the main trilogy) his/her impact/legacy will forever remain in the series and lore. Any and all future games will recognize such a important character in possibly different ways.
I would LOVE to play a future game where it's years after he/she died, and nobody even remembers or acknowledges Shepard ever existed. All his/her accomplishment's having been credited to various myths and legends, or mere obscured details that cover the truth (like maybe some people believing Shepard was Asari or Krogan, or that it was actually the actions of one faction that did those things).
Because in the end, how many heroes go on to live a happyily ever after and get everlasting fame? I'd rather see a aftermath where like most of real history, heroes are nothing but what we read in books written by others, or exaggerated stories told by those in awe at what was done by such people.
And thus...my strangely long rant about something I really couldn't give half a crap about at the end of the day. Which evidently won't/shouldn't affect someone elses opinion's, nor should they give half a crap about mine.