I don't totally agree with the Cloud as an anti-hero concept, to be honest. You make it sound as though saving the planet is not important to Cloud at all; rather, the world's lucky that the planet being saved would be a function of Sephiroth's defeat. However, the dialogue you cited conflicts, as I see it, with other instances following the restoration of the 'real' Cloud.
Quote:
Cait Sith: By the way, Cloud. What are you going to do now? Don't tell me you're
going to leave the ship?
Cloud: ......I'm the reason why Meteor is falling towards us. That's why I have
to do something in my power to fight this thing.
Barret: Good!! Then you're gonna keep fightin' to save the planet!?
Cloud: It's like you always told me, Barret.
Barret: Oh, uh, you mean that!
Red XIII: What? I don't understand!
Barret: There ain't no gettin' offa this train we on! The train we on don't make
no stops!
This segment, almost immediately following his recovery, at the least hints at a feeling of responsibility for everything that's happened. It also, however, seems to suggest a heightened interest in saving the planet.
Also....
Quote:
Cloud: Hey, Cid! What're you doing!? There are generations of knowledge and
wisdom inside the Materia. We're gonna borrow their powers and save the planet
from Sephiroth. There's no way that we can lose the Huge Materia. You understand
that, right?
Cid: Yeah, I understand. I understand that Materia is precious, and also
understand what you're thinking. But listen. I don't give a rat's ass whether
it's science or magical power. No, I guess if I had to choose, I'd rather put my
money on the power of science. Humans who used to only roam around on the ground
are able to fly now! And finally, we're about to go into outer space. Science is
a "Power" created and developed by humans. And science just might be what saves
this planet. I was able to earn my living thanks to science. So to me, there's
nothing greater! Now quit your worrying 'bout what Shinra's gonna do! I don't
want to regret not having done something later.
Cloud: But, Cid......
In this segment, Cloud mentions using the materia to save the planet. Further, preventing the destruction or loss of the Huge materia would seem to indicate an interest in preservation of the planet independent of Sephiroth.
Soon after, while in space:
Quote:
Cid: Don't worry 'bout me. Hurry up and go! If you don't hurry, the rocket's
gonna crash into Meteor!
Cloud: ...I can't go without my friends.
Cid: You @^#*%$&......! No time to worry 'bout other people!
Cloud: I'm gonna do whatever I can.
Cid: You're stupid. You're really *&^%$#@ stupid. Tank Number 8 blew up...... So
Tank Number 8... really was malfunctioning...... Shera... You were right.
But, ......this is the end for me.
Shera: Don't say that, Cid.
This is an example of Cloud as a trraditional hero, refusing to abandon a teammate (and, more importantly, a friend).
Later on, in the same conversation where Cloud states that his main purpose is revenge:
Quote:
Cloud: I know why I'm fighting. I'm fighting to save the planet, and that's
that.
But besides that, There's something personal too... A very personal memory that
I have. What about you all? I want all of you to find that something within
yourselves. If you don't find it, then that's okay too. You can't fight without
a reason, right? So, I won't hold it against you if you don't come back.
Cloud may be fighting to settle the score with Sephiroth, so to speak, but he's also fighting for the planet...and for Aeris.
Regarding ending sequences....
There is an ongoing argument as to what the Lifestream duel (between Cloud and Sephiroth) really entailed. Some people cite it as a physical conflict; others as an emotional or spiritual one. Whatever the case may be, however, is it certainly a representative victory. By defeating Sephiroth, Cloud can ultimately complete the process of throwing off Seph's malignant influence and emerge as his fully true self.
Ultimately, Cloud strikes me as a very human hero. Further, he is arguably the most complex hero the series has yet developed. Although he has many positive attribuutes, he also has weaknesses, primarily self-doubt. In the end, Cloud is able to overcome those weaknesses. He is certainly not the same type of a hero as, say, Ramza or Zidane. However, Cloud seems to me to be a better hero than that. He is representative of everyone; he has virtues and flaws, and we can all hope to, like Cloud, overcome our flaws and emerge as bettter people. Cloud may start out as an anti-hero, to be sure. I just don't see him concluding the story as one.