Well, it’s a little more complicated than that. I know that Flamethrower and Fire Blast have both been reduced in power slightly in X and Y, and I’m not sure how people are reacting to that, but in the older generations people didn’t consider Flamethrower “entirely superior” at all. The way it’s generally seen is that by multiplying power by accuracy you can get an estimate of the amount of damage a move will do on average, and if the less accurate move is still stronger, it’s worth it. Using the 5th generation numbers, you’ll usually do more damage with Fire Blast: 95 x 100% = 95 for Flamethrower, but 120 x 85% = 102, which is a bit higher (contrast Thunderbolt/Thunder, where Thunder’s much lower 70% accuracy means that, on average, you’ll do more damage with Thunderbolt unless you have rain support – 120 x 70% = 84). The 6th generation numbers give a similar kind of result. The reliability of the 100%-accurate moves can be attractive, but more powerful moves also have a better chance to one-shot an opponent, which can be extremely important (and, of course, there are a couple of Pokemon who can learn Flamethrower but not Fire Blast, like Electivire and Zoroark, but they’re kind of a minority). It’s also much easier to run out of PP when using Fire Blast, especially against opponents with Pressure. As a result, Fire Blast is generally preferred, but there’s room for personal taste. Honestly, I’m totally okay with this balance.
The values you suggest give us 60 x 100% = 60 for Flame Burst, 90 x 85% = 76.5 for Flamethrower, and 110 x 70% = 77 for Fire Blast. Flame Burst is still so much lower that it’s not really worth it, while Flamethrower and Fire Blast get values that are much closer together, so it’s harder to pick a clear winner, but people would probably still use both. I think making the ‘reliable’ option so much weaker would just make things much more frustrating, to be honest.
Pokémaniacal 