If we understand "skill" as the ability of a poker player to read people beyond the cards and "grind" the profit, then 7-C-Stud might be the game that recquires the most ability.
You're not waiting for a lucky hit in the "flop" to determine your strategy and you're definitely not praying God for a nice "river" card, as in TX Hold'em.
But if you understand "skill" as the ability to adapt to different games within a game, then Hold'em recquires of far more ability to play, not only your hand, but the hand of the other players. As Wilheim accurately states, the pre- and post-FLOP strategy are different...
My personal choice if I want to grind is 7-C-Stud, it allows for a "people-reader" to figure out other player's pattern of behaviour sooner in the game.
If I'm in the mood of being extremely aggressive and un-friendly, then Texas Hold'em is a good killing game... You can bait a guy by losing a couple of previous hands and then set him where you want for a head-shot... lock him in and shoot when he finally says "all-in"
But I just learned to play Tx H'em, I wouldn't know much. But as they say there's only two kind of poker players: "readers" and "read" or "rounders" and "rounded"... I hope to become a good reader some day...