Over the years rules have changed drastically, that and technology development have made the biggest difference when it came to on track duels. With the years it became more and more difficult to overtake someone on the track, you can't really blame that on the drivers but that's the way it is. In Senna's era, and I don't mean just Senna but Prost, Mansell, etc., things were different. Pit stop strategies weren't so important as they are today, races were a lot more intense and interesting, the driver factor was the most important thing, that's simply a undebateable fact.
As for the legend I believe it's true. Senna is kind of like Maradona, immense talent and skill, plus a controversial character. People like that become legends. I'm not saying Schumacher isn't that, he's one of the greatest, but the sport evolved and became something different in the highlight of his career. Personally I don't like what it had become, or better yet what Ferrari's(Schumacher's) dominance done to it and I rate 2 titles in a time of unmatched competition of the 90's the same as 10 titles won in the new Millenium.