Which is the best online game ever

It depends on what type of games you like. If you like Role-Playing Games, then World of Warcraft is pretty great... but you have to pay a monthly fee. One of the best free ones is Runes of Magic. If you prefer arcade type games, then Bejeweled is a very fun one. Word games... Scrabble, or Bookworm is pretty good... Facebook games, strategy games, card games... there are so many options, and top choices in each category.