I haven't read this whole thread, don't have the time(My internet is out on my main computer and I'm doing it on a friend who wants it back soon), but I will now counterpoint your points, TC.
Point 1)
First off, TONS OF PEOPLE PLAY POKEMON OF ALL AGES. There are full grown adults going on Smogon.com and debating D/P pokemon as we speak. They have made Pokemon into a very competitive game for many people to enjoy. and D/P Wifi only made that better, giving them a reason other then battling friends to EV train and breed.
Secondly, Rukario does have importance. He was one of the first fourth gen pokemon to be shown, he STARRED in his own movie, is gotten in a way few pokemon are(From someone else, without trade and in an egg) and Rukario hasa unique typing.
Point 2)
You forgot all of Rukario's TM/HM's and Egg Moves.
How do you know it would be overpowered? You can't really judge overpowered at this point because we don't know ANYTHING about the Metagame. For all we know, Pit's Up-B could be overpowered.
And he brings PLENTY unique to the table. For example, I'll post a link to my moveset...
http://smashboards.com/showpost.php?p=2511284&postcount=744
Close Combat's effect is completely unique, Flash Cannon is unique, Brick Break's EFFECT is unique, Earthquake is only similar to DK's Down-B, but different due to the no keeping it up and the fact that mine sends out shockwaves for longer range, Vacuum Wave is fairly unique, Force Palm is unique and Rock Smash would be the first throw that turns one around, methinks. Also, by your definition, Luigi brought nothing unique in SSBM, just kicks, chops and ONE fire based move.
I cannot deny it, your Squirtle moveset IS unique. The only not unique ones are: Nair, Dair, USmash, Dash Attack, Neutral A, UTilt and UThrow.
Point 3)
Yes, the last two pokemon have been from Ruby and Sapphire. They have both been pokeballs. They did Deoxys to quell all the people saying he would get in and Groudon because he is one of the two pokemon on the cover of Ruby/Sapphire.
Saying that putting a Fourth Gen pokemon in would "Complete Reject the Fact" that there is a third gen is like saying putting Twilight Link in "Completely Rejects the Fact" That there are other links like OoT link and Original Link. Or that putting in 3-D Mario "Completely Rejects the Fact" that there is a Paper Mario.
Point 4)
"Crutch like a movie"? In that case, Mewtwo shouldn't get in because his whole storyline pretty much took place in the movie. Or Mario shouldn't get in, his only claim to fame is video games!
Snubble didn't have anything close to a starring role and Munchlax is actually asked for, but he also has Anime appearances and the fact he was one of the first released 4th Gen pokes on his side.
Yeah, Rukario's role kind of stunk. But you CANNOT DENY it is a STARRING ROLE. He even had his name in the title.
Yes, Mewtwo had a better role then Rukario in the movie, had a better storyline.
Yeah, he was the original last pokemon. But, he is already practically gaurenteed. He has his movies, the last pokemon, the evil and all. Though it is easily arguable to say that Rukario and Mewtwo could both get in.
So there's my counter to my arguement. Feel free to rip it apart, I'll be back when I can get on again or when my internet is back.