I'm actually one of those who likes Unova's starters a lot as well, but here's my thoughts on each region.
Kanto: They are all reptilian-based, which seems a bit uncreative to me, I love having diverse designs among the starters, not to mention how overrated as heck they are. Also, Charizard is my least fave final evo of all the starters so this is why Kanto is at the bottom of my list, and even more funnier I never even used their starters compared to the later regions.
Johto: I do like the Cyndaquil and Chikorita lines, but Totodile is probably my least fave Water starter line. Also, my main problem with these starters is that their movepools aren't as great as the others, although I admit I did have a better run on SoulSilver by choosing Cyndaquil over the other two.
Hoenn: The first starters I ever used, I was alright with the designs, but Mudkip's line was my fave of the bunch due to the fact it was my first ever female starter in a Pokemon game. All three do have solid stats and movepools so they aren't terrible imo, heck even Blaziken became the first starter to be kicked up into Ubers thanks to Speed Boost.
Sinnoh: This was the first starter trio to all gain secondary types when they evolve, which did help give extra coverage when building teams in 4th Generation. Turtwig was a bit too slow for me and I'm not really a fan of turtles. I did love Piplup and Chimchar though because of their good movepools and type combinations when they evolve.
Unova: Now this is the one where I loved all the starters, along with being one of those few who actually likes the Tepig line. The designs were great, and I loved the concepts behind them (Snivy's line being influenced by Europe, Tepig's being influenced by China and Oshawott's being based on traditional Japanese samurais) and I was never dissatisfied with any particular one, and not to mention Oshawott is my fave starter ever!
Kalos: While their evolutions aren't revealed yet, I am liking the designs of all these three and the fact that it's also the first starter trio to not have any reptilian-based members. Tbh when I first saw Chespin, Fennekin and Froakie I was so confused which one I wanted to choose when I eventually play X & Y.
So, in my order of preference:
Unova > Kalos > Sinnoh > Hoenn > Johto > Kanto