We have had a lot of generic crew in this game. I want to see what you people think about them and their uses. Here's a list:

Weapons Engineer

Gunner

Mercenary Co-Pilot

Intel Agent

Recon Specialist

Sabotuer

Navigator

Flight Instructor

Tactician

Systems Officer

Tail Gunner

Bombardier

Hotshot Co-Pilot

Operations Specialist

Inspiring Recruit (me in a two-word description)

Courier Droid

I also want to know what's best to fill up Lambdas, TIE Shuttles, Decis, Upsilons, and Firesprays. What's good in swarms, what's good for bombs, what combos do you like?
These cards have been sitting in my desk for a long time now and I want to actually use them.

Not including Epic crew. I'm still working on that list.

Depends on the meta, depends on the ship. THere's no better answer than that, some crew options will be good in some places, others less so, and many combo with non-unique ones. You've also failed to include the faction-specific generic crew, K4 and Outlaw Tech, and Fleet Officer and Systems Officer.

Hotshot Copilot and Gunner is an obvious combo, Gunner and Ops Spec ditto. All three is great, but the only ships that can take all 3 commonly don't want some or all of them.

This is really too general a question to give a meaningful answer to, especially when your stated goal of 'filling up' crew slots isn't necessarily a good one.

There are at least two groups: one should always be considered, the other not always.

Always to consider, in my opinion:

Gunner, Intel Agent, Recon Specialist, Tactician.

Personally I‘d include HSCP, Inspiring Recruit and Operation Specialist, but I don‘t think they are as clearcut.

So whenever you have a crew slot, check whether these 7 are good for your list.

Recruit definitely isn't an always. It's only worthwhile if you're routinely double stressing yourself.

Tactician probably isn't worth it without an expanded arc of some kind.

Gunner is probably the most reliably useful generic crew, but even that is meta dependent.

3 minutes ago, thespaceinvader said:

Recruit definitely isn't an always. It's only worthwhile if you're routinely double stressing yourself.

Tactician probably isn't worth it without an expanded arc of some kind.

Then they are easy to check

By the same token, Tail Gunner is pretty much only useful in 2 ships: The ARC-170 (the ship the upgrade comes in) the Firespray (and probably best suited to Scum Kath Scarlett).

I think it SHOULD work with the Ghost, but rules as written currently say no.

16 minutes ago, Yakostovian said:

By the same token, Tail Gunner is pretty much only useful in 2 ships: The ARC-170 (the ship the upgrade comes in) the Firespray (and probably best suited to Scum Kath Scarlett).

I think it SHOULD work with the Ghost, but rules as written currently say no.

The Ghost doesnt need a boost thank you very much.

3 hours ago, BadMotivator said:

The Ghost doesnt need a boost thank you very much.

How so? The way I see it, a highly coveted crew spot going to tail gunner is probably bad squad management, so I think you overestimate the level of a boost of permitting tail gunner to work with the Ghost's auxiliary firing arc.

Breach Specialist also counts as a generic, but only helps one standard ship chassis.

1 hour ago, thespaceinvader said:

Tactician probably isn't worth it without an expanded arc of some kind.

Tacticians don't need an expanded arc, but they definitely get better as you add more of them. The old Panic Attack list (three B-Wings with E2 and Tactician, plus a Gold with R3-A2 and Ion) were absolutely horrific against aces back in the day. The B's could cover a very large area with guaranteed stress, and could then converge on the stressed target with saturated stress coverage.

Weapons Engineer is the only crew for Shara, Operations Specialist is a great fit for Rebel Fenn, Gunner allows a stress Ezra to double stress a target, Courier Droid allows you to deploy the usually PS4 Captain Rex alonside your high PS aces without giving away their location and makes a triple Scurrg list deploy at PS8, and Inspiring Recruit really helps AP-5's ability go off or pairs nicely with the Rage EPT in an Auzituck.