I hate to point this out, but the title really should have had a Question Mark on the end. Anyway, onto the main point.
Many people complain about Sinnoh, although it is by far my favourite region out of the four I have played, since I have yet to test Unova/Isshu. For now, I have to say that Kanto is my least favourite. Just as Para-Dox said, it does become rather repetative due to the fact you spend most of the time wandering around in circles. Still, I do love the region, but it remains my least favourite. On another note, Kanto severely lacks unique qualities when it comes to Grass-types, which happen to be one of my favourite. Most of them are Grass/Poison type with almost all of the same attacks, with the minor blips being Exeggutor and Tangela, the later having little power in main combat due to its somewhat low stats.