Without including FE:LH, I'd say spot on, though for me the order is different:

1.Master of Magic

2.Civilization IV

3.Colonization

4. Galactic Civilization II

5.Alpha Centauri

For me, I think FE:LH would probably fit in around 2.5 on the list...

lol, sry for the typo.

I did not play SOTS for very long but I really liked their take on diplomacy. Like you could build sentences and communicate specific ideas to the AI leaders.

 1. Heroes of Might & Magic III(I consider it a 4X)

 2. Civ IV

 3. SMAC

 4. Gal Civ II

 5. Civ II (nostalgia at work here)

1. Distant Worlds
2. Civilization (I)
3. Master of Magic
4. Master of Orion (I)
5. Civilization IV

I haven't played as many 4x games as some of you, but if I use 'willing to put some work into the game, to make it easier/more scenarios for me to play, by making handy references, scenarios, mods, etc. as one of my yardsticks, as well as how often I go back to said games...

Sid Meier's Alpha Centauri/Alien Crossfire - would love to see an updated version, as long as it stayed as true as possible to the original!

Ascendancy - made my own printable tech tree for this game, as the one I found online didn't have enough info for my tastes.  Still holding out for a PC port of the new IOS version...

Pax Imperia (yes the old Mac game, not the Eminent Domain sequel for PC).  Haven't found a PC port of the original game, so I haven't played it in a while... I do have Eminent Domain in a box somewhere, but it's not the same...

Galactic Civilizations II Darklords/Twilight - love the ship design feature!  I feel very little need to tweak/mod the game, which is a compliment to the designers!  Was playing TOA just yesterday...

Warlords III - Reign Of Heroes/Darklords Rising (don't play it as much these days as it won't work on my Vista machine despite numerout attempts to get it to work, I still have an XP laptop that I use specificallty to play this game when I get the itch).

BTW, in general I'm not a fan of non-turn based 4x games.  I enjoyed Homeworld when I played it, but not enough to want to play it over and over.  Warcraft wasn't bad either, but my reflexes aren't what they used to be.  I enjoy pondering my decisions, not just making them on the fly.

Also, I got bored with the Civ franchise.  SMAC/SMAX got a few additional concepts right IMHO, and I haven't been able to enjoy 'vanilla Civ' since (own 2 and 3 currently).  I got Civ 4 for Christmas a while back, tried it, and then gave it away... Civ 5 has failed to interest me, mainly because learning a new way to do the same thing as the older games gets tedious after a while (this is why I ended up giving Civ 4 away).  I'm just burned out on Civ in general, SMAC/SMAX excluded.

Elemental (E:WOM, E:FE E:LH) isn't quite where I'd like to see the game at this point.  I enjoy it to a point, but a number of elements just aren't quite where I'd like to see them.  So while I do like to play it every so often, it doesn't make my top 5.  It is well designed at this point, but as I mentioned,  just isn't quite to the point where I feel the need to play it all the time.

FreeOrion currently has my attention.  Still very much in alpha/beta mode, but I like how the game is put together so far.  I like it enough that I've made my own reference materials for it, to better understand the game.

Pandora - First Contact intrigues me, mainly because of SMAC/SMAX supposedly being a strong influence.  I may or may not pick it up.

The order is largely not important for me.

-Master of Orion II. The very cornerstone of a "space" turn based 4X. It had every element you have come to expect from these games.

-Civilization I. Because it made me buy a PC in the first place. In reality Civ II. Because that is how you do a sequel. That is really how you do it!

-GalCiv II. For the depth and longevity.

-Star Wars Rebellion (Supremacy). NOT turn based, but with (for the time) a fresh take on real time dynamics. And interesting use of unit cards, with various interaction and deployment.

-Heroes of Might and Magic III. Because they had Opera in the City Screen.

Honorable mention:

-Ascendancy. It had a weak AI, but I'm just going to put it up here, for the impression it gave me. If there is a digital soul out there, this one came close. You had no idea what was out there. Really.

1)  Alpha Centauri -- deep and philosophically inclined, has yet to be matched in this regard by any strategy...

2)  Sins of Solar Empire: Rebellion -- gameplay is extremely streamlined and easy to learn, excellent UI, faction diversity and unit counter system is solid

3)  Civilization V -- Excellent UI and gameplay, one of the few games that has successfully made late game interesting, offers better replayability than most games due to all the different civilizations, maps, victories, and player choices...

4)  Galactic Civilizations 2 -- Excellent lore and factions, solid gameplay

5)  Civilization IV -- Gameplay was good (though not as good as Civ V), built in mods were very cool, had strong replayability...

1. Master of Orion II
2. Civilization IV (the apex of the Civ series thus far; V just doesn't measure up though I really like the hext tiles)
3. M.A.X. (Mechanized Assault & eXploration)
4. Galactic Civilizations II
5. Sword of the Stars

Not sure if being an RTS instead of a TBS disqualifies a game from being a "4X" ... if not, I might toss Homeworld in there somewhere.  

1. MoM

2.Birth of the Federation(with player created patch)

3.Civ 4

4.SMAC though I never got to play alien crossfire, when I tried SMAC again after many years I couldn't find a version that had AC as well. All were
   just SMAC.

5. Here I place all that have their value, but do not go in the above slots. Moo2, Empire, GalCiv, Warlords series,

In no particular order, except for the first two:

Alpha Centauri

King of Dragon Pass (arguably the strangest TBS/RPG hybrid ever made)

Master of Magic

Civ IV (with mods, especially Realism Invictus)

Crusader Kings II

Sry Double post...

For some reason on this forum I always mix up the Edit and Quote button. dont know why.

Had forgotten about the Warlords games! Used to play the very first in the series by hotseat, with a friend. On the Amiga it must have been! I still got all of the boxes for all of those games, including the separate scenario builder for Warlords II! Yes, yes. Definitely up there with the most solid of them! Good clean fun!

I played probably about 5 of them alltogether, so its tough to judge, but from those i played, i guess i liked the Pax Imperia: Eminent Domain the most. I kinda liked Ascendancy too, but mostly for its atmosphere and music, rather than gameplay, i am not much into TBS games. The only one i ever played was HOMAM II.

I dont consider Sins to be true 4X, therefore i dont include it in my evaluation. If i would, it would be absolute No 1. on that list, its probably my fav game ever (even though the likes of Homeworld, Conquest Frontier Wars, CnC series, NHL series, FIFA/PES series and few others come close...)

Speaking of TBS 4X, did anyone ever played a game called Fallen Haven? I recall reading its review back in 97 and being fascinated by it (and the screenshots) - but never got to play it myself.