Please, share your thoughts on who you think were the two or three most useful squadmates in each of the original trilogy games, and why, if you're up to it. For me, it's like this:
ME
1. Garrus - Tech powers super-effective against geth; specializes in the two best weapons (assault and sniper rifle); has a fair amount of defense and durability due to Medium Armor and Electronics; his tech powers allow him to decript storage lockers and fix the Mako outside of combat
2. Wrex - Biotic powers excellent for crowd control; assault and shotgun specializations mean he does a lotta damage; Fitness, Barrier, and Heavy Armor make him nearly unkillable; his abilities are especially useful during the final fight against Sovereign-Saren
3. Tali - Tech powers, again, super-effective against geth; they also allow for decryption and Mako repairs; Electronics provide extra layers of shields; Shotgun specialization gives her good damage potential
ME2
1. Thane - Shredder Ammo extremely useful against organic enemies (most enemies in the game), like collectors and husks; Warp does good damage and can take down defenses; Throw is good for crowd control, especially if Throw Field is chosen; specializes in sniper rifles, allowing for great damage potential and taking down enemies from afar
2. Miranda - The Cerberus Leader power-up buffs the health and damage for the whole team; Warp and Overload basically allow her to take down any kind of defense; Warp and Slam do good damage, making up for the lack of strong weapon specializations
3. Garrus - Wields the two best types of weapons in the game, allowing him to specialize at all ranges; Overload, Concussive Shot, and AP Ammo highly effective against a type of protection each; Concussive Shot and AP Ammo additionally good at disabling enemies and increasing weapon damage
ME3
1. Javik - Has biotic powers that serve a variety of purposes, from damage, to incapacitation, to crowd control, to stripping barriers and armor; plus, they also allow for easy biotic explosions, even if he were the only biotic on the team; specializes in assault rifles, for which he also has a skill that increases weapon damage; has two team-buffing abilities, depending on choice, either increasing the damage and force of biotic powers, or decreasing the shield-recharge delay
2. Garrus - Again, specializes in the two best weapons, allowing for efficiency at all ranges; AP Ammo increases damage even further and is super-effective against armor (which a lot of tougher, more dangerous enemies have); Overload strips shield and is effective against synthetics; CS is highly effective against barriers, and can knock down opponents; Proximity Mine especially effective since it only activates if an enemy is actually close by it; his team-buff ability also increases the damage of all powers, instead of just tech or biotic
3. Tali - Drones excellent for offensive and defensive distractions, taking away enemies' attention while doing damage at the same time; Sabotage allows for control of synthetics, even if protected, which is especially useful against Cerberus' turrets and mechs, turning their advantages into your own; Sabotage also useful against organics due to disabling weapons; Energy Drain strips shield and barriers, and damages synthetics while restoring her own shields, combing damage-dealing and survivability; has a shotgun in case enemies get up-close and personal
Of course, this is just my opinion. What do you think?