Yeah, the difference ins pretty big. I'm guessing if you just look at the pictures there's not much difference, but that goes for Kick Off vs Kick Off 2 too. If you kept up with the Sensible Soccer series, you will know there's significant improvements in gameplay over the differerent games. The game actually changed a lot more than Kick Off.
Oh and Goal! shouldn't even be included in the Kick Off series. But you could add a lot of the extra Kick Off games, and why do you keep forgetting Kick Off 3 and Kick Off 96 and such? They are a part of the series. Which means there also was a lot of Kick Off games. Sure the gameplay changed a LOT after Kick Off 2, but was it for the better? At least, Sensible only got better. If only the original Kick Off 2 was improved upon instead of completely giving up what made the game so good.