Excellent gameplay, brilliant story, but lacking in everything else including an ending that seems to make sense.
Remember back to Mass Effect 1, the sheer amount content was staggering, Missions, Weapons, Armour, Abilities, Weapon Mods, Exploration and Morality choices. The shooter action scenes left some things to be desired but weren't awful in any sense, ME1 was an RPG with Shooter Elements.
ME1 story focuses on a Human marine (Sheperd) on a mission to stop a rouge agent from bringing the end to galactic civilization by bringing back an ancient threat known as the reapers.
Mass Effect 2 expands on many of the features from ME1, for the most part offering improvements, better more action oriented combat, great introduction and decent plot and many new enhancements and features, however the game lacked many of the RPG elements much of the immersion effects were removed offering fast travel in place of elevators, (to many players satisfaction), much more restrictions on weapons and armour and the dubbing down of exploration. However even with these changes ME2 was still a great game, while some of the core RPG fans disliked the chances, mass effect was always more focused on Action than Role Playing (with the exception of the conversational choices). ME2 allowed even more control of the universe with the players choices changing the major events. The changes to the gameplay make ME2 a Shooter / RPG with a higher combat focus.
ME2 starts with Sheperds ship (the Normandy) being destroyed and Sheperd going down with the ship, he/her is later revived by a renown extremist group to help investigate recent attacks on human colony's, that may be related to the reaper threat, with a new team and ship, The Normandy SR2.
Mass Effect 3 expands from the second game with no content from the first that was lost making a re-appearance to the series (with the exception of the characters). The plot from the previous games is continued, this time the reapers have finally arrived and earth being decimated as Sheperd and his team escape on the Normandy in an attempt to gather alien allies to help earth.
ME3 boasts an improved combat system heavily based uppon ME2s however with faster paced actions, and improved melee attacks, the player now has the ability to play within multiple floors of a combat zone, allowing for improved tactics, the AI has also been improved allowing for more exiting combat missions. The conversation systems within ME3 seems relevantly the same however the players choices have absolutely no effect on any of the major plot details whatsoever, while both missions and side missions still exist this definitely reduces the games RPG elements to a minimal, as the choices do effect weather some characters live or die and the events leading towards the end, but not the end itself, the removal of most mini-games (such as hacking, or bypassing) isn't a plus ether.
The games plot definitively deserves credit despite these changes however for its staggering ability to trigger emotional reactions, as characters that over the previous titles players have become attached to are drastically effected by events, for better or for worse, but im not going to say who, what or where, for that you need to play the game yourself. As i have said the players choices do not affecta the games end, however they do effect everything else, if a character survived the previous games they can be found within ME3, if not others are there to take their place and events do change, but most major decisions remain the same.
The new exploration system, while fitting is largely dull as you attempt to explore you are constantly interrupted by enemy forces that if they catch you triggers an automatic game over making everything more tedious than it has to.
The new multiplayer mode offers exciting new game play options, the game itself is similar to horde mode from Gears of War, it pits up to 4 players in a wave based survival mode for 11 rounds, until they can be extracted from the combat zone, these missions are plot wise based upon the actions of other units / races in the war vs the reapers across the galaxy.
Many have reported bugs with the game however i have found none, the DLC itself is not required to play the game, and honestly the player is not missing much by not buying it, that said if you are willing to get it i would recommend it even though all you get is a little galactic history, a few jokes and an alien version of Zaeed.
This review was not ment to tell you whether you should buy the game or not, simply to allow the audience to know why others are disappointed, however while the games end isent brilliant the game as a whole is, i would not like to see people ignoring a great game and series finale based on a single mistake that may be amended in the future.