Yes it was very successful. The mechanics introduced in gen 3 have been the new backbone of the modern games. It has been mastered since all the features removed in gen 3 (day/night for example) have been reintroduced and integrated with it.
The main reason imo that Hoenn is so controversial actual has not much to do with the region itself (aside from removed Pokemon/features) but the timing of the reboot. It happened right when the whole fad was blowing over, and people were losing interest in it. Perhaps thats the reason they did a reboot in the first place?
I'm glad they did something new though, as the Hoenn region is my former favorite region of them all. Its so natural and beautiful and I loved the theme of the games. I guess a good question might be what would have happened if GF didn't do a reboot? Would Pokemon still be here or would it be entirely different?
As for Black/White Unova has become my favorite region taking Hoenn's place. I loved Unova even more because it had more of a deeper coherent story that flowed well, the need to use only Unova's Pokemon was much welcome, and the timing of a reboot was good. Unova is like a remake/reboot of Kanto more than anything, but its unique enough to be its own region. There is also the fact that obtaining past Pokemon from the older gens is basically a non issue. Unova seems to build upon things as a reboot (like introducing seasons) as opposed to completely overhaul them.
The main difference between the two reboots is that one (Hoenn) has very drastic changes while the other (Unova) has more subtle changes. Hoenn as said before was a complete mechanical overhaul, but Unova kept and built upon the same mechanics and its a reboot mainly in its feeling. (156 new Pokemon, separated far from other regions, etc.) Overall, GF have learned from the past and have handled the second reboot a bit better.