Texas Holdem has become the popular poker game in casinos across the globe. Largely due to the fact that it is one of the most popular games on television and cable networks. Texas Holdem is hugely popular to play and easy to learn.

A bit more from Wikipedia:
Texas hold ‘em is the most popular poker game in the casinos and poker card rooms across North America and Europe. Hold ‘em is a community card game where each player may use any combination of the five community cards and the player’s own two hole cards to make a poker hand, in contrast to poker variants like stud or draw where each player holds a separate individual hand.
After slow but steady gains in popularity throughout the 20th century, hold ‘em’s popularity surged in the 2000s due to exposure on television, on the Internet, and in popular literature. During this time hold ‘em replaced 7 card stud as the most common game in U.S. casinos, almost totally eclipsing the once popular game.
