Personally for me, i'm a rather big fan of Tamers to an extent, as well as Adventure and 02 (I will admit i have not finished all Digimon series, i got half way though frontier and half way through Fusion, but the rest i have yet to watch. I have seen Tri though, can't wait for the next movie!)

As for a reason for Digimon coming to the Real World, i was thinking that a Virus of some sort infected the Digital World, and in an last effort, the Digital World ejected as many Digimon as it could into the Real World before the Virus could get to them.