In the Beginning!
Genki is a young boy with an ordinary, dull life. That is, until he gets a new game in the mail. He soon gets pulled in and must now fend for himself within the game. He soon comes across two friends, Suezo and Holly. But, will they be able to stop the terrible monster, Moo?
Aired 17/04/1999EP 1 - In the Beginning!

1999
Monster Rancher
Genki is a boy who loves playing video games. One day he's zapped into the world of Monster Rancher and meets the girl Holly and the monsters Mochi, Suezo, Golem, Tiger and Hare. Together, they are searching for a way to revive the Phoenix, which is the only monster capable of stopping the evil Moo.
(Source: Anime News Network)