Well, you can't have many Vikings against Zerg as they get demolished my Mutas and Hydras. And, no matter how many Marines you have, 20 Overlords will be able to drop a few Banelings and kill off your army.
Here is nothing about realism, by the way. In real life the Marines would split themselves, without any "control" from the general. In the game, however, they would just stupidly stand and shoot, ignoring the fact that 2 Banelings can bust them all. This is something that I don't like about RTS genre in general, and about such fast-paced games as Starcraft in particular: a lot of time you spend on things that your army should do itself. Marines' split, Ghosts' snipes, Marauders' and Stalkers' hit and run, Sentries' shield... It would be great if they all would do it themselves, saving you a lot of time to do the management stuff: teching up, taking expansions, etc.
Now, it is bearable to have these things done by yourself in relatively slow-paced games, like Age of Empires, or even Dune series. But in Starcraft, it becomes really tedious. Instead of calm play with thinking and observing the battlefield, you have to spend a lot of time kiting these 2 rushing Zealots.
I get the feeling that Jedi Academy was, like, say, Dragon Age 2, a game that was aimed to cut a lot of cash by using its predecessor's success. It was terrible unbalanced game. You are right, dual-wielding swords were too strong in that game, but not only them. Weapons were totally useless: they were weak in Jedi Knight 2, but they at least were a bit useful in such team modes as CTF, where one player could distract another player in a lightsaber battle, while his teammates shoot from the distance. In Jedi Academy, weapons were nerfed so much that they were literally unplayable.
Jedi Knight 2 was much better balanced, but, of course, players found some exploits and destroyed the game with them.
If it is 1000 Pikemen and 200 Cannons against 4000 Horsemen charging right in them, then sure, Horsemen would be slaughtered. If it is 100 Pikemen and 10 Cannons against 2000 Horsemen, however, there was no way Pikemen would win.
The only way people could defeat 10 times bigger in size army is while defending castle. Before 1400 or so, when siege weapons became really powerful, it was literally impossible to take castle in any way other than by attrition, even if your army is 100 times bigger. You just couldn't get inside.
I want a game where I don't have to react in nanoseconds in order to not lose half my army to some cheesy unit. Actually, Dune 2 did it very well: when a enemy unit gets close, you are warned and have, at least, a few seconds to scroll to that place and to arrange your units in a defensive position. It's different in Starcraft: you hear warning, click on the minimap - and see your army stormed twice by HT and each unit having lost half HP. Again, it is totally unrealistic: only insanely stupid and drunk people would just stay waiting patiently when they get stormed.
No way. Unless your opponent is so bad that he doesn't get the idea of splitting his overwhelming army in a few parts and send them to all your expansions. If you have 5 bases and your opponent has 2 bases, but he has 3 Colossi, 15 Zealots and 10 Stalkers and you only have 5 Marauders and 2 Vikings, you are dead.
Well, in Age of Empires, if you have 2 times less units than your opponent, you are in trouble too. However, there it takes an awful lot of time to destroy half the enemy buildings, especially castles and towers, so the player with superior economy, actually, usually wins, and there is not much his/her opponent can do, because there are no cheesy units.
Priests were really hard to control. They didn't have automatic attack, so you had to point every unit manually, and by the time you point the 10th unit or so, your priests are usually dead.
Unfortunately, EU4 was too easy, compared to EU3. Let's start with the fact that it is not RTS by any means. Then, it is so easy when you have some experience in it or EU3. It took me, I think, 100 years or so, starting as Denmark, to conquer half the Europe and to expand a bit into Ottomans and Russia. You have so much money in that game that you really don't have to worry about your army eating your resources: you can have a size of army 3 times of your supply limit and still not to have a very negative income. Also, unlike EU3, it would take really much expansion without any Casus Belli until the countries will start declare war to you. In EU3 it would take 1-2 small annexed countries to find yourself at war with half the world.
And, actually, EU3 was also quite easy, once you get a hang of it. Victoria II was far more complex. And Supreme Ruler: Cold War was more complex still.
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Actually, there is another great RTS many people have missed, I guess. It is Star Wars: Galactic Battlegrounds. Sure, it was just a copy of AOE2 engine with Star Wars sprites. But the campaigns were amazing, and there were a few new ideas as well: air units (too weak, but, still, interesting to play), Jedi who could both attack with lightsaber and convert. It felt like something between Starcraft and AOE, and also in Star Wars lore.
As a separate game, it is not that great as it is just a copy of AOE (very good copy, but still). But if you perceive it as an official AOE2 expansion, then this game really shines. At least, its single-player component.