It feels like a small step back from its predecessors in some regards, but it is still an exceptional game nonetheless.
Let my start by saying that Mass Effect 2 is one of my favorite games of all time. The combat, the characters, the story and how it is affected by the player's choices, all of these things have solidified ME2's spot in my list of favorites. No disrespect for the first Mass Effect, though, as that game made me a fan of the series to begin with. Naturally, I was more than a little excited to play the final installment in this fantastic series.
The good:
ME3 still has the intense, strategic combat of its predecessors. Choosing characters with a variety of powers is essential for maximizing effectiveness in combat. From the telekinetic biotic powers to the anti-synthetic tech abilities, each character has their own way of dealing with certain types of enemies, encouraging the player to switch up the squad when needed. The player has the option of playing purely in real-time by mapping buttons to specific powers, or occasionally pausing combat to bring up the power wheel and methodically maximize damage to enemies. Either way, the variety of enemies and battlegrounds make for many exciting skirmishes.
The writing and dialogue are also exceptional. Anyone familiar with Bioware games knows that these guys know how to write stories. There are a few lines that feel slightly awkward, but most of the dialogue is still topnotch. This makes it easy to care about the characters, which include everyone from the past two games (provided they are still alive).
The emotional impact of the cut-scenes and dialogue is made even more significant by the incredible soundtrack. I think the musical score in ME3 is the one aspect of the game that took a gigantic leap forward. It ranges from the typical sci-fi, electronic-type music you might expect from the series, to beautiful orchestral tracks that give incredible emotional weight to the scenes they're used in. If you have played this game already, I highly recommend getting the soundtrack, as it is one of the best video game soundtracks I've heard in recent years.
The bad:
As much as I like the characters in ME3, I felt extremely limited in who I could choose in my squad. Not including the DLC character, there are six possible squadmates to choose from, which pales in comparison to the twelve (the DLC characters were included in the PS3 version of the game) from ME2. And this may be from a more personal perspective, but almost ALL of my favorites (Mordin, Thane, and Kasumi) are not playable in ME3 (though they all make appearances). Garrus, another one of my favorites, is still playable, but it still seems disappointing to be so limited in who I can put in my squad.
Another part I didn't like about ME3 is how choices seem to have less weight than previous games. Since it is supposed to be the final game in the series, one would think that all the choices made throughout the game should have an effect on the way things end. This is, unfortunately, not the case. I will avoid all spoilers, but I'm sure most of you have heard about the outrage over the ending. Without giving anything away or sounding "whiny", it should be known that the ending is neither satisfying nor dependent on any choices made throughout the entire series. This discourages multiple playthroughs, as it makes most of the game seem pointless upon reaching the finale. Bioware recently announced that they plan to release additional content to add more closure to the series, but in its current state, it is just not very good.
All in all, ME3 is a great game. It's difficult to not base one's opinion of it on the ending, as the ending of anything is usually what sticks with us the most. However, the majority of the game is thoroughly enjoyable and incredibly engaging. I highly recommend playing the first two (or at least the second one), before playing ME3, as I imagine there will be quite a bit of confusion due to the numerous references to events from past games. It's hard to not feel slightly disappointed, as this game is supposed to be the conclusion of an epic story that started in 2008 with ME1's release. But despite its shortcomings, ME3 is a solid RPG, and definitely worth playing.