Jagged Alliance 2 is clearly the best. Some of the reasons:

- Enormous amount of detail, options and complexity in every aspect of the game but achieved with a very intuitive user interface

- Awesome strategic campaign. When you are fighting countless tactical battles you need to tie them together in an interesting way. Otherwise you'll more quickly get tired of the individual battles and find no reason to keep playing

- Character, personality whatever the correct word. There was nothing dry or stale about the JA2 world despite its realistic setting. From the laptop to the random NPC, it was oozing character.

Give me a complex but well designed game, with an interesting and compelling campaign full of interesting characters and I'll be more than happy.

Chaos Gate.

This is squad based tactical turned based combat done right!

I will go with Jagged Alliance 2 too. It has everything you'd want in a tactical game. From my knowledge, no other game has to date surpassed JA2's complex gameplay mechanics.

My favorite in the genre, other than the full on "tactical RPG" that is the best-game-ever Final Fantasy Tactics, is probably Night Watch (Nochnoi Dozor). Freedom Force vs Third Reich did well and was close to it -- except it had all the real time elements. As often as I paused and gave orders, the game really should have been a tacstrat. It'd probably be at the top if not for that. (FFvTR is on GOG.)

As I reread this, I guess I've preferred the ones that oozed setting and "fun" more than the strategy. I may not be your target audience.

Nice initiative, :o)

The first X-Com is still the greatest for me, Jagged Alliance 1 and 2 are good too.
Another one I kinda liked, but didn't got very good reviews, was Abomination, mostly for the post apocalyptic setting, which was not so much done then as it is now.
Oh yes, almost forgot about that one, Shadow Watch, was altough a bit shallow, good fun for a while. Commandos was never the game for me, altough I liked the setting, I felt too restricted in how it had to be played (I still must give it another chance). Baldur's Gate, a good deal of options, only thing I didn't like about it was that your squadmates could leave you because they find you too good or evil.

Any ideas? Uhm....

Give the player more options to deal with any given situation. If the objective is to retrieve something for example, perhaps sneaking is an option instead of a full scale assault, that sort of thing.

I don't know much else, try to be creative, good luck. ;o)

I've been pimping for this game all my life on this forum, but you may want to try Darkwind: War on Wheels if you're interested in doing phase-based, squad-level wargaming with vehicles/physics. An example of a modern, shitty TB squad-level tactical game:
http://www.gamersgate.com/DD-SSTA/star-sentinel-tactics (I still can't believe I paid for this rubbish)

Where it failed:
- loading screen is hilarious
- awful interface. I mean awful on the shit level. Doesn't provide enough info, too many ambiguous icons
- boring gameplay, slow animations. Even finding the last alien in X-COM wasn't boring, and I never thought I could get bored by a TB game. I don't even know where to begin with how hard this game fails, but the whole thing is just unexciting. There's no sense of tension, and there's no sense of satisfaction when you kill an enemy. It lacks the thrill of playing a tactical game.