In 2021, some of the best casino slot machines to play included popular titles like "Mega Moolah," known for its life-changing progressive jackpots, and "Gonzo's Quest," celebrated for its innovative Avalanche feature. Players also enjoyed "Starburst" for its vibrant graphics and simple gameplay, while "Book of Dead" captivated with its adventurous theme and free spins. Additionally, "Cleopatra" remained a classic favorite, offering enticing bonuses. These slots combined engaging themes, exciting features, and the potential for big wins, making them top choices for both novice and seasoned players alike.