1) Interlocking subgames (space, planets, melee, dialog)

2) Characters with a coherent identity spanning the subgames and additional touch points (lore, music, font)

3) Motivated exploration combining both points of interest and the vastness of space

4) Epic story line that unfolds thru extended play and encourages replay

5) Mix of pulpy and hard sci-fi theme and motif

I agree with Frogboy. xP

1. Have a personal story to tell.

2. Variety of aliens.

3. Explore the planets and the galaxy.

4. Electronic/ambient/synth music

5. Hence the story, write some characters that fulfill the story project.

1. Story

2. Exploration

3. Unique Characters

4. Aesthetics

6. Music.

I've never played any of the Star Control Games...     I was 12 when SCII came out... and by the time I was into computer games  MOOII, Diablo,  MechWarrior II were the games I found... and then in  college SMAC and Gal Civ 1 and 2 etc...

So it was before my time.

However from reading these forums and the UQM forums...

1.  Replayability   (to have people this ridiculously passionate about a game nearly 30 years later.. it has to have been replayable)

2.  Memorable

3.  Offer a sense of accomplishement

4.  Inspiring

5.  Nostalgic

I'm looking forward to the release of Origins.    Stardock does not  always get everything right (Elemental)... but they have always done right by their players and customers (Free copy of Fallen Enchantress for those who bought Elemental)  (not giving up and ending with a really great game in the end).   Also, it is obvious that Brad WANTS to get this right...  so for a game series to inspire so much passion in so many people...  I can't wait.

I'm only going to list one:

1.  Compelling Story.  The narrative hook was the best I think I've ever seen in any game:  You finally get back to Earth, after having been incommunicado for 20 years, and discover that it has already fallen, with the morale of its people near the breaking point.  And you have the technology to give them a chance to fight.  Less than five minutes in, and you're hooked.  I've introduced the game to a bunch of people, and as soon as they hear the arrogance of the initial Ur-Quan warning message, followed by the introduction "I am Starbase Commander Hayes of the slave planet Earth", they get visibly angry, and just can't put it down.

1. The wonder of exploring an unknown universe

2. Interesting and captivating initial contacts. Some clearly friends, some clearly enemies, but others?

3. The joy of hauling resources back home and upgrading your ship/fleet

4. The music!

5. Solving quests that have a meaningful impact on the rest of the universe (like gaining friends)

so...320x200 resolution with 256 colors?

For me it's the specific gameplay that SCII/UQM/Starflight introduced

1) Space exploration
2) Planet scanning
3) Planet landing
4) Conversation trees
5) Ship to ship combat

Without any of that you just don't have basic elements for Star Control.

Addendum:

6) Ripping off Starfleet Battles

________________________________________________________________________________

If it can be done that would indeed be awesome. A "classic graphics" mode.

Would probably be easier to backport Origins into the UQM engine.

1. An enormous, well-crafted world that makes you want to see more of it.

2. No in-game journal constantly pointing you towards the next objective, which requires you to pay attention to the dialogue.

3. Witty and deep conversations with lots of choices.

4. Non-linearity. Any direction you take must be meaningful.

5. A grand plot that is slowly assembled like a jigsaw puzzle, rather than lots of meaningless self-contained side quests.

And that's just the story and the dialogue. There are many more points I could list, including the graphics and the music (which contributed enormously to the immersion in SC2), or the aliens that are weird but logical in their own way.

1) Meaningful stories

2) Galaxy exploration and exploitation

3) Heavily developed NPC's. Alien races' in this case. 

4) Voice acting!

5) Player's personal investment.

I'm late to the party, and since most of what i consider Star Control to be Star Control have been mentioned storywise/gameplaywise/alien wise above already, i'll put down a few points not highlighted enough:

1.  Good mother ships and Good combat ships to choose from, the type that wants you to get in and Fly everytime you jump into your ship !

1.1: True to it's unique genre. Gameplay mechanics essential for making it feel like Star Control !

2. Space... the vastness of it, i recall the first time i opened up the starmap and was blasted away actually realizing every single dot is a Solar system filled with mysterious planets ! And that you can actually fly to it via free will through hyperspace and fully control your ship in realtime while doing so ! Which also gave you absolute freedom to cancel out autopilot and fly wherever you wanted to should you feel like doing so or to outrun an enemy in hyperspace. The sense of vastness was surreal. I hope SCO's starmap will provide that same experience.

3. HYPERSPACE and the MUSIC You cannot have the one without the other and you HAVE to HAVE both or it's not Star Control !

4. The planets and minerals on them and possible mysteries to be found on them.

5. Back to the ships.(some finer details) I hope we will possibly see damage effects and system failures on ships that have been damaged coming back from distant explorations. Some lights on ships will look nice such as nav lights)

6. The joy of hauling resources back home and upgrading your ship/fleet (which was said already but needs repeating)

Beta on Steam!
Release likely on September!