Uh, what? He got a Mega Evolution, an arc in the game introducing that mechanic (which very few non-Legendaries get), the marketing boy for Pokken, an important role in many spinoffs, among other things. How is that minor? Even ignoring that, how many Pokémon even come close to matching that?
Also, the fact that he remains popular far past his generation and is very popular even outside Kanto kind of shows that people not remembering him isn't true at all.
Actually, Mewtwo only had the movies as appearances in the anime unless you count the 5 second cameo in Kanto. Anyway, even though no one will argue Mewtwo isn't important to the franchise, you're severely downplaying Lucario if you think he isn't either.
Greninja surprisingly isn't really getting "milked" that much. Aside from Smash (which as far as we can tell, was mostly on Sakurai), he hasn't gotten anything special that Delphox hasn't.
Anyway, they're not really similar at all, at least not at this point. Lucario has been promoted far past his generation and has remained "relevant" in the eyes of fans and the developers alike in terms of popularity and marketability. A lot of people recognize him now, maybe not to the extent of Pikachu or Charizard, but he's definitely one of the Pokémon that people would recognize outside of the generation.
In short, you're severely downplaying the good points of the character and how he has lasted for almost the past decade.
You know what, I'll say this : Lucario is promoted and milked just like Mewtwo was back in the day. But for a Pokemon that only has aura and lasers to gain popularity, it's not really great.
But if we look at it, sure, Mewtwo and Lucario are similar. Both are super overrated, have a lot of fans, gets a lot of attention and are known by many. I still think though that Lucario was more builded to BE popular more than Mewtwo in a way.
Mewtwo was the best Pokemon for a long time. It's the last guy you fight, the strongest Pokemon that was created by mistake (2powerful4science), the Pokemon you want when you're a kid because he's really cool, but also hard to find. That's where the movies helped Mewtwo growing in popularity, to show how cool this Pokemon was and how you needed him. But after a while, pretty much after Melee, Mewtwo was gone. He reapeared in the remakes, but appart from that, Mewtwo was not shown a lot.
Lucario is different : he's easy to find (literally gaved to you by the champion in D/P/P), needs love to evolve, shoots beams, has a super expensive movepool to expand dongs and minds of kids discovring him, had a great design, and was promoted through a movie. To this day, just like Mewtwo, Lucario is used as the "Toy who can make new kids buy our stuff", appearing in the anime multiple times, having a mega-evolution to introduce new gameplay mechanics and many other things like this.
That the thing I don't like with Lucario. While Mewtwo was indeed promoted like crazy and is still overrated to this day, he was at least rewarding. They just don't give it to you like a toy. Lucario is a Pokemon who was made to be popular from the beginning, with no reward except having a Pokemon who looks cool. Profitting of the same promoting campaign as Mewtwo, Lucario is now popular like Mewtwo, but in my eyes, in a disgusting way.
And now let's wait for the debate to continue...
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