If you haven't played these, I advise you to stop reading now as it will make no sense to you whatsoever. Here's a few thoughts:

The War:

I'm guessing the warring sides were either countries or coalitions made up of countries. Slater served under Grice on Mars, and Hornton made the final fleet action orbiting Neptune. Grice somehow hung on to his units on Mars.

G-police 1:

Why did Hornton want to be transferred to Mars? Was it a hotspot, even more so than Callisto?

How did Nanosoft set Krakov up? Was it people from Nanosoft flying those Krakov craft in missions 11-13?

Why wasn't Slater killed for his abilities, if Slater minds saying so himself? Even before mission 10 (after which an anti-virus is worked on) he's not too bad.

What was the new romance Slater's sister hinted act? Was it Ricardo, did he somehow get close to her to help him crash her havoc?

Just as a point of interest, what a stupid time to have the venoms out of action - for one of the hardest missions in the game, the retaking of the HQ!

G-Police 2:

Whatever happened to Monmont?!

I reckon Grice deliberately had some of the codes on Mission 10 kept the same so he could paint a picture of the g-police to his units.

What became of the syndicate and the earth division? The syndicate had plenty of units at their disposal judging by their attack in mission 13. How long did the earth divisions temporary truce last for? If it ended when? Did they turn their attention on the syndicate or rejoin the mars division on leaving callisto, or before? Or did they do neither?

Mission 13: The marines stop attacking the base, then stop, then the syndicate attack, then stop, then the marines attack the base once again, exposing the raptor. Funny order of events. Also had those gunboats from the previous mission been kept for the attack, I reckon nothing could have stopped them.

If only the player was left in charge of that last fight, we could of had 'em easily!

I'm guessing the Talavera, Excelsior and Barrosa are smaller than capital class ships since you don't need to enter them to destroy them.

Generally:

Also what became of Krakov? Nanosoft kept going even as part of the syndicate. There were officials that escaped from the Karkov HQ before it was blown up, or were captured, what became of them? There are gunboats with a K on in the picture gallery in G-Police 2. Are Krakov part of the syndicate in g-police 2?

The presidents: Is Argenta killed when the Krakov HQ blows up? And who's the president of Nanosoft?

I'd love it if there were further sequals, with the battle on Mars and then the war against the syndicate on return to Callisto. Sadly it looks like there won't be