Digimon World (for the ps1), doesn't have the best graphics, but it does have the best digimon experience possible. It's a tremendously goodgame.
Other then that, i suggest the Rumble Arenas... They're short and do not have many digimons, but they are extremely fun, and i had a blast playing them when i was a kid.
But other then those no... there isn't any good digimon games out there...
The digiworld 2 was too rpg like wich kinda ruined what could be a great set of a serie, digimon world 3 was kinda good... it grabbed good elements from D.W.2, and provided a much larger world, filled with much more story in a chibbit cartoonish way... unfortenatly there are so many loading screens that it will break the pace of the game, and the leveling system is rather weak... you would be needing to train a LOT just to have decent digimon... DigimonWorld 4 was... a real wtf... digimon with swords.... /facepalm...
If they picked up digimon 4, took out the swords, introduced the leveling system from DA2, the variety of DA1, used the gameplay of DA4 and the story of DA3, they would have the perfect digimon game....
Oh well... and the MMO, takes all your freedom to move around, has no story and you can only choose between 3 digimon's... (i think they promised more digimons, but the game has so many cons, that the pros are now worth it).