I've seen bad AI in modern games too, while Warlords 2 for example had some of the best AI. Maybe it depends on the genre a bit.

Camera... Many old games had a fixed or a horrendous camera.

Really? I am playing Warlord Battlecry 3 recently and the AI likes to attack with small groups of units periodically and after I beat the first wave the rest is just free level up material. Warlord Battlecry 2 AI is better or it is a different game we are talking about?

That remind me of another sin.

Broken Path-finding.

In many old RTS your units won't go where you tell them if you click a long distance from where they are. You have to click next to them step by step.

Or when the units in the front hold up because attacking enemies or the road become narrower. The units at the back will break rank and find some other path, splitting up your armies.

Also when a group of units is attacked. Units near the edge of the group will break ranks to pursue while the rest of the group stands idly by, splitting the army again.

Different game. Warlords 2 is turn based
http://www.mobygames.com/game/warlords-ii
It's not real time like Battlecry.

The good AI is even noted on Wikipedia, though I personally can't vouch for any other than 2 which I played.
https://en.wikipedia.org/wiki/Warlords_%28game_series%29#Original_games_of_the_series

The "attack periodically with groups" seems to be the standard AI strategy in RTSs. Not sure how is it now, since I haven't played any recent ones. But that's why while I can play very well RTSs vs PC (Warcraft 3, Starcraft, Red Alert), I don't survive long vs human opponents.
Is RTS AI different now? How is it with Starcraft 2 or Grey Goo for example?

That said, if you play against the PC you will always find anti-AI methods that will work. As long as they offer a fairly good challenge I'm happy.

Horrible default keybinds.
System Shock 2 for example.

only bad userfriendliness at getting games running.

setting of ems memory, ports for sound card, .bat file and so on.. i was dull for it

This is probably a matter of taste and many will disagree, but:

Since old games came with printed manuals and were limited in their resources and file sizes, they often didn't care about being self-explanatory. What's this story all about? What's the goal of the game? What do I need to do? What can I do? How does this work? What keys do I need to use? I don't understand a thing ... Well, RTFM! :P Personally, I'm very glad these times are over. When I play a game in my spare time, I want to be able to jump right in and have fun without any kind of time-consuming preparations. Granted, some games can really bore or annoy the player with their intrusive in-game tutorials as well, but the better games allow you to learn the rules while playing, without you really noticing it.

Despite my clear preferences, I also have to add though that the issue mentioned above is much more problematic now that you don't even get printed manuals anymore. Having to read pdf manuals before playing or ALT-tabbing out of the games to consult them is evern worse than playing with a printed manual in hand.

The lack of keybind customisation. Though that's an issue with some new games as well, so nothing has been learned.

Also, generally sucky control layout and choises in many old games. Like Redguard for an example, which I tried to play, but just couldn't bother to continue, as there's no possibility to put the camera rotation on mouse and the control layout is just ackward.

Now that is a game that's basically impossible for me to beat. Even after trying hard to memorize every traps and enemies I only manage to get to pyramid, level 2 perhaps?

I bet the developer was a sadist

Lots of icons/buttons with obscure symbols.

The first task was to find out what each and every odd symbol was for, usually it was not enough to just try them, but you needed to actually read the manual and memorize them.

Ok I don't know if this was specifically a problem with Bullfrog games, as in their games I felt this quite often, like the Populous games, Powermonger, Theme Hospital, Dungeon Keeper, Magic Carpet... Somehow this annoyed me specifically with Bullfrog games for some reason.

Here are some from classic RPGs:

Permadeath, particularly in games with non-random dungeons. This is especially an issue in classic Wizardry. Basically, the game randomly deletes characters in certain circumstances, and it is clearly *not* a bug.

Weak healing: It's one thing to have healing be so weak it's useless during battle; it's another (and far worse) thing to have healing be so weak that, even if you return to your base of operations, healing is quite tedious. Examples of this are (again) classic Wizardry (at least until your Priest learns MADI) and the game Pool of Radiance (only healing spell is weak, rest doesn't heal HP significantly, the Fix command from later Gold Box games is absent).

Unfair death traps: Might and Magic series has some of these. Sometimes, examining a barrel gives you a permanent stat bonus (got it on the wrong character? time to reload, and you don't know about this ahead of time); other times, it can kill the character examining it. Even worse, you can have traps that kill your *entire* party. Even that isn't as bad as a certain trap in Might and Magic 2: Take a certain treasure, and your party is permanently crippled, and the effect isn't immediately obvious, so it's easy to save (over the game's only save file) before the effect is noticed. That is not fun.

Note that those are just the ones in early RPGs; once you get to the Baldur's Gate era, you have a new list of "deadly sins" to worry about, but that's beyond the scope of this particular post.

I am not, how you say, technically inclined, but that seems like a not-good thing. :P
(Also, should this not have made it a 'Silence Blaster'?)

I think you miss small. "attack with small groups of units periodically"

That's a difference between the AI building up a big group with armies that synergised each other and the AI setting the rally point of their barracks to your base.

I only play the campaign of Wings of Liberty of Starcraft 2 so I don't think I am in a good position to talk about the AI. Likewise Grey Goo. I had been pampered by RTS with level up mechanics that motivate me to micro to keep them alive. Normal RTS without level up mechanics does not hold my interest long. No point keeping them alive, just march them to the meat grinder that is war.

I will take Sins of a Solar Empire as an example instead.
The only small group of enemies the AI will sent against you is scout. And the AI do that to scout your base before attacking. If the AI think you are stronger at the planet they will not attack you.
I know that because the AI does not attack me when I had the bulk of my armies park at the planet. When I shift them to a neighboring planet the AI comes knocking.

When the AI think it is outclassed it will run and adept its strategy. For instance the AI was routed by my Star-base, the next time it comes it will bring anti-structure ship to take out my star-base. It will build more flank ship when I have a lot of carriers (anti fighter / bomber of carrier)

While the AI is nowhere the level of human and have to cheat in resource to be a challenge, it still provide a fun enough challenge.

Unforgiving adventure games. You miss one little thing in the beginning and end up wandering aimlessly through a great bit of it not knowing it was all a dead end.

Also:

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Brrrr Chunka Chunka Chunka Brrrr... Chunka

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Gahhhhh!!!!