In case you are interest, I visited my top 5 from Mass Effect 1 here. I did the same sort of top 5 list for Mass Effect 2 as well.
Mass Effect 3:
5) Shepard's Dreams
Early in the game, Shepard sees a small boy on three different ocassions. It starts innocently enough, with the boy running around and playing, but then later hiding in a vent during the Reaper attack. Later Shepard sees the boy getting onto a ship that gets shot down before it can escape. Shepard has seen so many lives lost over his adventure, and this boy is an innocent victim the embodies the incredible burden Shepard has to carry. Later in the game, Shepard has a handful of dreams haunted by a misty, often colorless landscape where he hears the voices of people he has lost along the way as he tries to catch up to the boy who continues to elude him and always winds up engulfed in flames at the end. Perhaps not quite the same surprising impact of Mass Effect 2's introduction, but it creates a strong emotional connection to Shepard's weary psyche.
4) Mother Thresher vs a Reaper
Threshers were big and scary. They made quite an impact on me, and were part of my first top five moments list from the first Mass Effect. So, what happens when you introduce the mother thresher? For starters, the caverns leading up to this scene were creepy using dark lighting effects, a bit of wall-written mythology and frequent rumblings from all around to set the stage. Once you emerge from the earth, you see a Reaper in the distance. How can you defeat something like that? You can't, but this massive thresher can and does.
3) The final run
Say what you will about the ending - and plenty of people have - but that last run through the broken streets of Earth toward the beam of light that will take you to the Citadel was pretty awesome. The Reapers just keep throwing more and more at you. Desperation is in the air. Hope is slipping away at every turn. The odds have become more than overwhelming. It is a dark, it is oppressive and in the end when the Reaper's beam nearly wipes you out, Shepard picks himself up and staggers forward with one uneasy step after another and just his pistol left in hand.
2) Lost loved ones
Shepard faces loss throughout the series. In the first game you lose either Kaidan or Ashley, and you can lose Wrex as well. The second game can end so badly that technically Shepard even dies then - but you can also lose almost all of your crew and still win. I went with a default game in Mass Effect 3 - I did not yet import any of my other ones, but I have read enough articles and spoilers to know that you can lose different members or your party at several different intervals. Who did I lose in Mass Effect 3? Miranda was not my favorite character, but she sacrificed her life to save her sister. I chose to aid the Geth - I sympahtized with their plight when their history was revealed to Shepard (in a cool sort of virtual reality stage). I did not expect that choice to wipe out all of Tali's people - nor for her to commit suicide as a result by falling off of a ledge. And then there is Mordin - one of my favorite characters from the second game who sacrificed himself to save the Krogan race and encourage them to join Shepard's battle. In his own words: It had to be him. Someone else might have gotten it wrong.
1) The ending!
I know a lot of people think the ending is rough, but... Yeah, I'm messing with you here. We'll blame it on being so close to April Fool's Day. The ending is pretty rough. It just did not meet expectations, more so than it was out and out horrible. I could not resist capping the list off with the above statement, so now I give you my:
Real 1) The camaraderie
There are so many examples of this it is tough to know where to start. Whether it was playing a game of chess with Traynor, or spending time with Cortez at the memorial, watching Ashley try to recover from a hangover or witnessing the relationship between Joker and Edi play out - there were a lot of really great moments. Aside from the ones listed above, there were a few others that really stood out to me, and they almost need their own list, so here goes.
- 3) Garrus and James. While Vega was not one of my favorite characters by any means, his banter with Garrus on the ship at one point had me cracking up as the two veteran soldiers continually attempted to one-up one another with taller and taller tales. They end it on an amusing note where they talk about how they save the universe from the Reapers. Garrus concludes with something like: with a little bit of help. James again goes for the one-upsmanship and says: Nah, just us. Mostly me.
- 2) Liara joins Shepard in his room and shows him the video log archive she has been creating, just in case their team doesn't make it. You get the chance to tell her how you want to be remembered, or you can ask her to put it in her own words. Liara's own words are incredibly flattering and show the deep friendship between the two.
- 1) Garrus and Shepard on top of the Citadel. Garrus has been along for the whole ride, and by the time you are ready to wrap up Mass Effect 3, he and Sheppard have shared a lot of battles and time together. They have a quality moment where they have a shooting contest on top of the Citadel. You are given the choice to aim straight, or miss on purpose. I chose to let Garrus have the win, and his excitement afterward was very rewarding.