Personally, I would really like to see Dishonored, with all four of the pre-order DLC packs with the Dunwall Trials. Dishonored is a fairly recent game, and is scheduled to have two more DLC packs to be released sometime this year.

In addition to this, Human Revolution would be another good pick in my opinion. It is a good game and would help complete GOG's selection of the Deus Ex series.

*Dishonored
**Backstreet Butcher Pack
**Shadow Rat Pack
**Arcane Assasin Pack
**Acrobatic Killer Pack
**Dunwall City Trials

*Deus Ex: Human Revolution
**The Missing Link
**Explosive Mission Pack
**Tactical Enhancement Pack

Alpha Protocol
**Stealth Pack
**Assault Pack

Armed Assault II (Wormholewizards)
**British Armed Forces
**Private Military Comapny
**Army of the Czech Republic

The Sims 2
**Happy Holiday! Pack
**Family Fun Stuff
**Glamour Life Stuff
**Happy Holiday Stuff
**Celebration! Stuff
**H&M Fashion Stuff
**Teen Style Stuff
**Kitchen & Bath Interior Design Stuff
**IKEA Home Stuff
**Mansion & Garden Stuff

Probably ArmA. Their DLC always optional, but high in quality. It's nothing more than a "thank you" gesture to the developer.

I'm not against this type of DLC.

*Ahem* http://www.gog.com/forum/general/now_that_gog_sells_dlc_which_newish_games_would_you_like_to_see_here