Sorry to overreact, but Gemmell stirs my soul, he makes me laugh, makes me cry and he changed my life. If you would try one more, try Ravenheart. It's doesn't hold back on the action but in my opinion the character development is so strong, even for really minor characters. And the climax is breathtaking (that would be the one which makes me cry).
Overall people love his work so much because it makes us believe we can be better. One of Gemmell's favourite anecdotes is from a letter he received. A man had just been reading some of David's work and was out walking is dog, his head full of heroes. Lo and behold in the dim dusk light he sees two men attacking a girl. Mr Dogwalker shouts, let's his dog off the lead and charges, and the men run off and the girl is unharmed! The point of the letter was that if he hadn't been reading Gemmell that evening, he simply would have walked on by.
He makes us believe we can all be heroes!