Starcraft 1's AI received extra resources only on "Insane" difficulty, and that was only accessible with the map editor. It is not normally a thing in game as there were no difficulty settings (hopefully they'll change it with the remake) The AI in melee doesn't receive extra resources but it doesn't need to scout and always knows where your things are.
I actually don't think it was bad. The only problem was the horrendous exploits in unit control but it was strategically fairly sound considering it had to be written before the meta was developed.
The insane AI received infinite resources, and thus a lot of people didn't like it because it was basically playing a different game. When I modded the AI, my default version wouldn't be able to beat any experienced player at all (though it was able to trounce the default AI, casual players, and even the cheating insane AI without any resource cheats of its own), so I also made one that got a resource boost from time to time. Despite this, the non-cheating one ended up being popular despite me starting the obvious. Now, granted most of my stuff got downloaded by non-english speakers so I never really knew what they were thinking.

We also did some "deity" level AIs with absurd bonuses which were mostly ignored. But my sense is that people don't like playing with things that are artificially propped up, nor do they like ones that just swarm you with units early on and that's it. I set it to it only performing aggression about 20% of the time, with some ridiculous forward base strategy 5% (note to firaxis, that's about as much as you should forward settle), so to keep people honest, but not so they could just mindlessly build units/defense at the start. Because that's boring.
Starcraft 2's AI does not cheat at all until the highest difficulty of which it starts a gathering bonus. It also has to obey the Fog of War. Blizzard did state it cheats, however it doesn't in-game therefore it barely beats Firaxis in the race to terrible documentation. (Why is explaining how your game works such a outdated concept?)
Both AIs are highly exploitable and not a challenge to veteran players so naturally much like in Civ I don't think AI bonuses are too unreasonable. I mean, making an eports level AI is not even something I would think is reasonable.
And yes, as stated before, Blizzard doesn't make good AIs. That's sort of an aside though....
Beginner players often have idle buildings and floating minerals because they forget to make more units, especially while doing other things. The AI can be many places on the map at once and be programmed to react as soon as each units is produced, while the player cannot. This may not be cheating in a literal sense, but it does provide advantages that the player cannot attain. These advantages do not exist in a turn based game, where the player's ability to manage things quickly are not tested.
Well, beginner players in Civ build useless buildings, have poor tech priorities, move units inefficiently, make bad purchases/don't make them at all, and sometimes don't pay attention to various things. I mean, obviously they aren't going to be penalized for not clicking fast enough, but it all boils down to efficiency and game knowledge. In theory people have infinite time to take care of all these things, but I will just say that I often neglect a ton of things despite this.
To me it's all the same thing, and also something an AI should be able to do better than a beginner.