It's a wee bit elitist to say that Sensible appealed to those who couldn't get into Kick Off. Kick Off isn't a "hardcore soccer game" any more than Sensible is. Dunno how you got that idea. Sure, Sensible is easier to pick up and play, but that goes for games like Civilzation and Pirates! too. I think the "easy to get into, hard to master" rule applies to Sensible.
On a sidenote, I had played Kick Off a lot when I played my first game of Sensible. Kick Off 2 was me and my brothers favourite two-player game, and we had gotten pretty good if I can say so myself. Actually, when I play it today, I have no way of getting back into form the way I was back then, when we recorded Golden Goals and such. I also played a lot of Player Manager. But when I got Sensible Soccer (the first one ever), I liked the game, but I had my doubts it would be as popular as Kick Off. I was pretty wrong of course, because giving it some time I turned myself into one of the biggest fans of Sensible ever. So... it's not because Kick Off 2 is a harder game people like Sensible better. That's stretching it.