Its shortcomings are overlapped by the game's epic conclusion to an epic trilogy.
There has been franchises where everything that happened in previous installments mattered in the final part, but Mass Effect takes that and turns it way up. Everything you did in the previous 2 parts, every decision made, every romance ignited, really matters in the final part; and that adds to the enrichment of this trilogy's story. Most of the weaponry from ME2 are back, including all of the stuff from the DLC's of 2. The same also goes for the return of Zaeed & Kasumi--provided they survived, just like rest of the "suicide squad" that defeated the Collectors in one way or the other.
The shooting part is nicely refined, with a wide variety of enemies that require different means of quickly dispatching them. Sometimes, you'll want a heavy weapon and plenty of Warp to dispatch a heavily armored foe. Other times, you'll want a strong tech to deal with shielded foes; or just a strong, hardy soldier to blow the crap out of the enemy.
Graphics and audio are fantastic, and first-time players will quickly realize that everyone, including your own version of Commander Shepard, will get or have gotten quite the makeover. The voice acting is great, especially when it comes from the mouths of voice actors like Mark Meer, Martin Sheen, & Jennifer Hale. The sound fx is also good, and players will quickly realize when a Reaper is firing its high-energy kinetic beam soon enough.
There are, of course, a few shortfalls in the finale. Aside from the occassional glitches, the minigame of scanning for resources or quest items while trying to evade the Reapers' attention is not like hacking or bypassing a console in 2--a sort of "Mass Effect Pac Man", if you will. It can be real harrowing to scan for that one quest item that could help ready the galaxy to fight the Reapers, and evade incoming Reapers that are faster than the Normandy; and then have to wait awhile before the system is clear again to retrieve them. The other shortfall, though not as much, is multiplayer. While it is nice to boost galactic readiness by playing ME3's version of Horde Mode or Beast Mode in the Gears series, using a wide variety of stuff and characters, it really isn't needed, as most of the replay value, for most players, will come from the different ways of completing the epic--if just as lengthy as 1 & 2--single player campaign.
Despite those shortfalls, ME3 delivers one of the finest finishes to a game franchise's main story. It may be disheartening to make the toughest decisions that would seal the fate of the Mass Effect Galaxy to some, but when you think of how far your Shepard has gone from being a simple human special ops space soldier to a human that shaped the future of the entire galaxy in a rather short amount of time, then you'll likely see just how epic of an experience the entire Mass Effect Trilogy is. ME3 may be the end of it all, but to those who love these "RPG Universes", it's only just the beginning.