The best one for me is Ngcup98 (Sidekick 3 1/2)
Sidekick1: old skool camera angle, the gameplay isn't very fluent and has an horrible ingame music. (CPU controled player change only)
Sidekick2: Debuts the new game engine, The camera angle changed. The controls of this game are awful, not even the CPU has full control of the player. (It has manual player change but it sux)
Sidekick3: Most of the bugs in Sidekick2 are solved, the game play is much more refined in this game, blah blah... I agree with everything takumaji said about it
(The manual change player works in this game)
Sidekick4: Would be the best one if wasn for a new charge bar feature, the bar charge when you have control of the ball, when it reaches 100% you can do a very powerfull kick. It ruined the game, everything now is resumed to run with the ball for awhile and kick , 99% of the time the result will be a goal, the cpu is too dumb to take the ball from you. It destroyed the game.