I prefer Digimon, I like the aesthetics more and the games have largely maintained a constant level of quality in my eyes. Pokemon's still cool though.
Also, what about Monster Rancher?
There were 4 Digimon World games released on consoles with many on handhelds(even a spiritual successor going on the PSP), but the games have never really gained much popularity, partly due to Bamco's incompetence.
It's a shame, because I thought Digimon World 1 and 2 were both much better than any Pokemon game I've played.