Crew at the end of Mass Effect 2
Here's a useful flowchart that shows what ending you'll get based on your choices in the game.
(Click for full-sized version)
Yes, it is possible to save all of the crew. You need to recruit and perform Legion's loyalty mission last, after completing everybody else's loyalty mission, as well as upgrading your ship's armor, shielding and main weapon, so that you go through the Omega 4 Relay as soon as the crew is abducted.
The suicide mission has 3 parts: Infiltration, The Long Walk and Final Battle. In order to have the best possible ending, you need to take the following choices:
Infiltration:
- Specialist: Tali or Legion or Kasumi, if you have the DLC
- Fire Team Leader: Garrus, Jacob, or Miranda
- Your team: Anybody else
Long Walk:
- Biotic: Samara/Morinth or Jack
- Fire Team Leader: Garrus, Jacob, or Miranda
- Escort: Mordin - if you do not send him back with the crew, there is a good chance he will die later on
- Your Team: Anybody else (I usually go with Legion and Thane, but that's just my choice)
Final Battle:
- Your team: Anybody who's loyal (I usually go with Legion and Miranda, 'cause I love seeing her give lip to The Illusive Man and Legion is just awesome)
If you have performed everything correctly (all your allies are loyal and went through the Omega 4 Relay the moment Shepherd returns to the ship after the crew is abducted) and made the correct companion choices in the Suicide mission, everybody will survive.
Good luck!
Reference
You need to go after the Collectors immediately after they capture your crew to save them. If you do any other mission in between, you'll arrive to late. This means you should wait with the Legion mission until you've done everything else, and then after Legion joins your crew you need to immediately perform his loyalty mission.
There are several factors that need to be fulfilled in order for everyone to survive the suicide mission:
- You need all upgrades for the Normandy
- All crew members need to be loyal
- You need to choose the right crew members for the tasks during the suicide mission
- For the ducts: Tali, Legion or Kasumi
- Fire team: Garrus, Jacob or Miranda
- Biotic shield: Samara or Jack
- Fire team 2: Garrus, Jacob or Miranda
You should let Mordin escort the saved crew back to the Normandy, he had a high chance of dying otherwise