I loved all of the companions from across the Mass Effect series.
(Except for Jacob, because he's a complete tool and an utterly squandered opportunity for a fun, interesting character that ends up going absolutely nowhere.)
However, the problem with such a massive cast is that ultimately... it spreads things out too much, and it becomes patently aware when you realize, for instance, the amount of content characters like Garrus and Liara get compared to ones like Zaeed or Samara.
Let's do a comparison, shall we? In this case, I'll use Tali and Samara.
Tali:
Relevant Mission to Advancing main Plot in ME1
Always Acquired
Side Mission in ME1
Cameo in early mission in ME2
Acquisition Mission (Optional)
Loyalty Mission (Optional)
Integrated role in Rannoch Arc (Possibly Dead)
Joins Crew After Rannoch Arc
Samara:
Acquisition Mission (Optional)
Loyalty Mission (Optional)
Ardat-Yakshi Monastery Single Mission (Optional)
So yeah. Two squadmates, and one of them you can potentially never even meet.
To make myself clear, I am NOT bashing any character, at all. I like Tali and I'm glad for how much content she got. I like Samara and wish she'd had more. The problem is we have a HUGE cast. 6 in ME1, 10 new ones and 2 recurring in ME2, and 3 more new ones in ME3. I love 'em all, but there can be no denying it, some characters got way more love than others because there was just plain not enough room.
Like Miranda and Ashley. Two characters, both pro-human... both serious at their jobs. Jacob and Kaiden, both laid back biotic drinking buddy marines... Samara and Thane, both parents with issues with their kids, so irrelevant to the story it's possible Shepard never even meets them. The fact is a lot of these characters are redundant. They're all unique and special, sure, and again, I'm not bashing any of them or saying the series would be better off without one of the ones you liked. But if we had a smaller cast, each of the characters that remained could of been given more attention, definitely.
If Bioware can deliver a huge cast and keep all the content even across the board? Hey man, I'm all for that. But in games, things inevitably get cut. I would rather have a moderately sized pool of companions with focus and relevance to the overall story (in ME2, the only character actually tied to the overarching plot was Mordin, for instance), than be teased with a bunch of characters I end up liking, and then getting sad when the ones I like most or think have the most potential (Zaeed, Samara, Kasumi) get shoved to the wayside.
Keep it focused. Sometimes, less is more, and more is less.
Just my opinion, of course!