I voted for Omaha. I like to play it and after a long time practising I have had some good results recently. Of course, because there is more NLHE about this is the most "popular" variant.
There used to be a mixed game on
pokerstars, it was PLO/NLHE. This was a good variant, however, I don't see them much at all now? Used to be a selection in Home Games Club as well. Now it has just disappeared.
I have a variant in mind. Mixed tournaments, but with not so many variants as HORSE or 8-Game. How about a PLO/ NLHE and Stud, tournament. This would please most people, Obviously, this would be an aggressive form, however, for those who prefer a slighly less aggressive game, we could have PL08/ PLHE and Stud Hi/ Lo, although I think the length of this game would be 50% longer than my original thought,