I have to say, Hoenn has some pretty unique Pokemon in its own right.
My fave starter line of this generation, and for good reason. I remember starting with good ol' Mudkip when I played Ruby for the first time and it remained a strong battler throughout the game. What made mine more unique was that I ended up with a female on the first try, before I knew female starters were rare. Swampert can both tank a hit and dish the damage out and has only just one notable weakness.
I used to never like Absol, but as time went on it grew on me and thanks to its Mega Evolution that came in X/Y I now love Absol because I just learned how powerful as an attacker this thing is, and with Super Luck it can become a great critical hit abuser. I definitely like its unique design.
One of my fave Psychic (and Fairy) lines ever, and they only got better come X/Y. Gardevoir surely was a really fun Pokemon to use given it's a powerful special attacker that starts off pretty damn weak but the effort into training it early does pay off once it becomes Gardevoir, who is now also among the strongest non-Legendary Fairy-types too.
I liked the theme of the Lotad line, and how they managed to incorporate its unique type combination (Water/Grass) into it as well. It's got a notable niche as being one of the few Grass-types that utilizes the rain thanks to its abilities' effects activating in rain. I guess that may be why I eventually started liking Sapphire's version exclusives over Ruby's as time went on.
I know its stats suck but I actually love little Masquerain's design. Those eye-shaped antennae are definitely its fave feature on it, and would explain its Intimidate ability. I love how cute it looks and sadly it's not getting the love it deserves.
One of my other fave Hoenn Water-types. While I never liked Huntail or Gorebyss much, I do like how adorable Clamperl itself on its own can look. Again, I really think it needs more love because I love the design of it and that cute face on the "pearl".
My fave of the two final stages of Wurmple's line, because I think it looks way more beautiful than Dustox or even Butterfree (but not as beautiful as Vivillon imo). I also love how Beautifly's Pokedex entries tend to portray it as threatening for that cute appearance. It's really funny when I look at those.