That's because more of today's game are being made with super-bosses and secret bosses that are hard to find, and you need extra tough weapons that are hard to find as well. It is a bit disproportionate for those super-secret bosses to be a lot more powerful than the main bosses in the game, but it allows those that just want to finish the game to be able to do so and those that want to take on the extremely hard challenges to be able to do so too.

In regards to FFX, I think that they took this a little too far [SPOILERS]with the monster arena having super hard creatures and Yu Yevon being comparably easy. I think that FFVII had the right mix between the final fight with Sephiroth and the two weapons.[/SPOILERS]