Depending on what your definition of best offers is, American Express can offer credit cards with extravagant benefits and perks. However, most American Express credit cards carry an annual fee, and not all merchants accept American Express.
As much as capital one offers great rates, I find them to be in competition with discover cards. You can occationally find lower rates through your local bank and near holidays.
It appears that American Express credit cards have levels of rewards on their cards. Rewards/benefits depend on the card that you have and the usage of the card.
"American Express offers several tiers of cards. For personal cards they offer the Gold, Platinum, and the Premier cards. For businesses, they offer the Gold, Plum, and the Platinum."