If the number of pages available is the sticking point, Jim Lee is your man. When he retires his pencils, he'll have done a lot less comic work than Jack Kirby. I have the feeling that Lee likes comics but he doesn't live and breath comics.
Well, it's not like Kubert and Infantino and Williamson and Wood all got together, voted, and decided Kirby was their king.
He became Jack 'King' Kirby because Stan 'the Man' Lee put the nickname in place. Jack was tagged 'King' because his last name started with a 'k'. If he'd been Jack Firby, Stan might have named him Jack 'Flaming' Firby, the hottest comic artist around. Although, you probably wouldn't be saying "He's not Jack Firby. They call him 'Flaming' for a reason."
Kirby is gone and Kirby was great but not all of his work was great. When people speak about his major creations, Captain Victory and the Kirbyverse don't figure prominently in the conversation. Those pages aren't cheap, though, so you'll still be dropping a decent amount of coin if you add C.V. to your collection. Over time, you'll probably make money with either Lee or Kirby.
At the end of the day, like Pete said, buy what makes you happy. If it climbs in value, all the better.