Barret stood up for an issue that really hits close to home: Maybe drilling into the planet and sucking out energy might sometimes have some negative consequences. Barret (the first and most stereotypical black Final Fantasy character) and AVALANCHE (Square is still trying to figure out what that acronym means) opposed the evil/extremely evil Shinra Corporation, for equal parts destroying the planet and attacking his hometown. Now, I'm not advocating anything here, but if anyone wants to replace their arm with a gatling gun and take down a destructive company whose drilling has caused irreparable harm to the environment, I'm not gonna get in his way.
Sonic really didn't have much of a choice in fighting the evil Dr. Robotnik. He had to free his fellow woodland creatures from being forever turned into robot henchmen. It was either that, or live in constant fear of someone bumping into him causing dozens of rings explode out of every orifice of his body. It also helped that Robotnik unwisely chose to make his flying boss machines out of a metallic alloy only damageable by spiny hedgehogs and flying foxes.
The Lylat system had been taken over by a disembodied monkey head. The Cornerian army had all but disappeared. All that remained to oppose Andross's innumerable forces were some forest animals with access to space jets. Luckily, Fox McCloud (whose family comes from Space Ireland) was just angsty and heroic enough to barrel roll his way to freeing the frequently-conquered planets, despite the best efforts of his crew to annoy him to death. Weirdly, the ending ceremony reveals that the Cornerian army was around the entire time! None of them were able to help, however, because Andross took over the galaxy while they were all on shore leave (probably). The fact that he could have just waited a week to have an army help him out makes Fox's lust for liberation all the more admirable.