A virus is a microscopic organism that can replicate only inside the cells of a host organism. Most viruses are so tiny they are only observable with at least a conventional optical microscope.
Recognized by the Guiness Book of World Records as the MMO with the longest play time per player, and easily the oldest game on this list (launching four years ahead of World of Warcraft, way back in 2001), Runescape deserves mention because it's one of the most updated and popular games of any kind on the planet.
Skyrim(and other elder scroll games like morrowind) is probably the longest. I wouldn't say it's the best but it was pretty addictive. Witcher III is also pretty long with lots of side quests and things to do apart from the main quest. The sims(and other games like sim city,civilization V,crusader kings etc....) have infinite replayability . The Dragon age games are also very long. If you want long games,play Rpgs, because they're the longest games.