Okay, here is my opinion....
Civ IV is not a bad game, but doesn't keep my interest for too long either. Civ II and III (although I couldn't stand III at first, now is my favorite to date
) are more fun to play.
1. Battles, the way it's set up in CIV is utterly preposterous, worse than in Civ III. When every single unit has a single strength, it leaves no tactics, tactics went out the window. It's a simple matter of building the type of unit based on it's modifier percentage for what you need (swordsman for city attack, archers for city defense, etc). Now this is okay... but this would be better (and I was hoping Civ IV was going to be like this)...
- give each unit a seperate attack and defense factor (as in Civ III)
- and give each unit greater abilities vs. certain types of units, or a specific unit (as in Civ IV)
- these greater 'abilities' vs certain units could be categorized based on offense and defense
- keep a 'unit health' factor of some sort
- promotions were a great idea, and they should keep these so the player can individualize each unit
that is not really a groundbreaking idea, yet brings tactics to a whole new level. This way, defensive type units like spearman would still have a bonus defending against horseman (mounted units) but would fare much better at defense than at offense (since the sight of a bunch of spearman chasing mounted warriors around is quite ridiculous, so in this case, a spearman should not get as much of a bonus vs mounted units on the offense). It is really this simply, and they would have a battle system capable of almost anything. They should add some other things, such as after a certain point, a unit is no longer effective at all (so spearman dont take out tanks), although this was mostly solved in CIV, due to the chance being so far apart, unless the tank was badly damaged.
- if they use their imaginations, they could set up something such as the ability for units to create battle formations (armies as in CivIII), or keep it the same as in CIV, whereas the attacker faces the toughest defender.
They need to fix the modern era units, aircraft, and navy... these have been an absolute mess. Bombarding from a distance works better than suicide cannons. Aircraft need to be more powerful and be able to sink ships, and destroy ground units (not all but some, otherwise they are next to useless to build). The aircraft carrier needs to eventually replace the battleship as the main naval power in the modern era, with modern destroyers, and cruisers for protection, with a higher use of missle systems (since that is how it actually is) and air force to project power.
The modern era of combat has completely changed, this could easily be implemented with the above combat system (simple mix of CivIII and IV), giving all special forces, marines, armed forces, etc their individual strengths and weaknesses. The modern era should be 1 of the more exciting times to play. And this would force the player to not just make tanks, but to make a variety of forces (since tanks alone will get slaughtered, and do require combined arms to be successful, which has been proven time and time again).
I actually have not tried in Civ IV telling your war allies to attack a certain city, not even sure if it works well, but I think they could expand this quite a bit, without too much difficulty... just another diplo option. Even SMAC had this option.
- and the BIGGEST THING, allow HUGE maps with the ability to field huge civ's! If someone does not want that, let them turn it off, or play a small map... but after Civ 1, 2, and 3... then in 4 you are stuck with a puny small civ on a puny small map, most of the time it's just hit 'enter', 'enter', 'enter' for next turn, I hope they go back to big scale!
- I hope they improve the terrain so it isn't just a mush of whatever it throws in there, and actually makes sense.
As long as they stick with the formula, of what made it great throughout the many years, I have faith it could be the greatest of all time.... and I hope it is, CIV got shelved after 3 months, back to playing CIII.