The original poker game was 5 card stud. If you have never played 5 stud, there is a reason why: it sucks and nobody plays it anymore. The game doesn't stimulate much action, because it is usually quite obvious who is winning. Eighty percent of your hand is exposed. So, along comes 5 draw to the rescue. Poker just got really interesting. Not only can you represent hands (and put people on hands) based on betting patterns, you could do the same with the number of cards drawn. More importantly, there was more action per street because you had no idea what anybody else had. Even with going from 4 streets to 2, there was more action. As a general rule in poker, games with more action become more popular than games without action. The other rule in poker is that games that more reward skill tend to become more popular than games that do not (as an aside, it seems that the opposite is true in home games.) Guess what? Seven stud has more action than Draw and it requires more card skills, primarilly due to the exposure of 4 cards in each hand. So seven stud was the game of choice for a while.
Then came Holdem. People were attracted to Holdem because it required some of the same skills as stud, but since the exposed cards are community property, there is a lot less to keep track of. It was basically a poor man's version of stud in that sense. However, it picked up a characteristic of Draw that 7 Stud left off: 100% of my personal cards are face-down. Thus, it was not possible to ascertain who was ahead based on cards. Bluffing became a bigger aspect of the game.
I have always suspected that the use of Holdem in the Main Event of the WSOP had quite a bit to do with Holdem's popularity as well.
Not all Holdem is created equally, there is of course pot limit, no limit and limit. Although pot limit was the norm in Europe, limit was the game in America, with only the high rollers in Vegas ever engaging in no limit. Card rooms preferred limit, because it meant the fish would lose slowly over time versus their likely fate in NL. The old adage is you can shear a sheep many times, but scalp him only once. Limit Holdem was played with antes, not blinds at first. This sucked, because if you can check around pre-flop, you will see 7/9 of your cards by the flop. Thus there was no reason to bet pre-flop without a monster. Blinds changed all this by stimulating pre-flop action. David Sklansky says that all poker starts with a struggle for the antes. Now that it is a struggle for blinds (which are proportionately larger than antes) the game got juicy.
The next big thing was Omaha, which comes in two forms: high only or "O/8" a.k.a. "Omaha High Low 8 or better to win." Of Holdem was the poker equivalent to a roller coaster, then O/8 was the equivalent of riding a roller coaster butt naked on crack without a seatbelt. There were some pockets were Holdem had all but died, including the Vic in London, Harrah's in New Orleans and a few other Mississippi river boats. Holdem's popularity in Texas was strong (perhaps due to the name) but those in the know (Card Player, Poker Pages, rgp, etc) would regularly write about how Holdem was going to die soon and Omaha would take its place. When I started playing "real" poker in 1998, it was at a cardroom that only dealt Omaha. I only learned to play Holdem when the club shut down and I was introduced to the FSC. At that time, FSC had a couple Omaha tables and 1 3-6-12 Holdem game. The Omaha tables were all booked up, so I played Holdem. I won (fyi, I had lost untold foturnes in O/8 to that date) and was hooked. But the wave of poker was clearly in Omaha's favor.
Then something happened that very few people expected. Poker became a television phenomenon. Everybody reading this knows all about that, but it was probably the single biggest boost to poker's popularity. Since only Holdem is played on TV, Holdem benefitted from TV the most. Now, it is hard to find Omaha games. The word "poker" has become virtually synonymous with "Holdem." I am guessing that all over America, young guys have walked into casinos asking to get in a poker game and when they sat down and saw 4 cards dealt they were completely confused as to what was going on.
Anyway, you all know what poker is like today, but I thought you would appreciate hearing how we got where we are.
Random thoughts from a lawyer, an accountant, a commodities trader, an ex-Marine and a WSOP Main Event money finisher that don't know as much as they wish they did...