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I like SMT, Dragon Quest, and Digimon.
The big difference though is that Pokemon has longevity. I've never put over 100 hours into a SMT/DQ/Digimon game but I have over 200 hours in every Pokemon game.
Pokemon just has more lasting appeal, multiplayer, competitive, a huge playerbase, etc. These other monster catching games are good distractions from Pokemon, but that's about it.