Seriously?
Good:
Graphics are great.
More weapon options.
Weapons actually have damage etc.
More appearance options.
Some emotional encounters.
Bad:
Storyline as times is confusing.
Story seem too focused on cerberus.
Options in dialouge are greatly reduced.
Paragon/renegade system revamped.
Useless armour sets.
Endings are terrible.
No damage res on armour.
No armours for squad members,
No way to increase squad stats.
Research removed
Overall.
Mass effect 3 makes attempts to move back to the RPG genre then takes steps away closer to a shooter, The game overall is very linear it feels like most of your time is spent running down a 1 way corridor or scanning on the map for war assests.
They claimed the thined out squad is to have more time with your companions but you actually get to spend less time with them than in any other RPG i have played. Some of the interaction that is there is good especially with garrus and liara.
The inclusion of multiplayer i ignored since they said it would not impact the campaign, that was an outright lie your galactic rating remains at 50% unless you play multiplayer and this reduce's every assest you gain in single player by 50% so say you gain a turrian cruiser for 70 points you only get 35 points.
You need i read 4,000+ points to get the "optimal" best ending options which bioware said could be gained without touching the MP but having done all side quests and gettings all allies aside fro mthe quarians i came in at just under 3,500 after my 50% deduction.
The ability to research squad improvments has been removed instead each of the 2 outfits the have has a single stat like +20% power recharge. Heavy weapons are gone in 3 missions you find 1 to use for a brief period but that is it and no explination as to why, yes grenades are back but they bounce about when they hit the ground now and usually end up hitting thin air rather than your intended target.
The endings as many others have said are just beyond terrible hundreds of hours playing Mass effect and the 3 endings are just criminal. =(