Big Mike said:What's your budget? And you when you say 'best'...do you really mean 'best (at any cost)'?
Any 10X zoom lens, like the 18-200mm will have to compromise image quality for the convenience of the zoom range, while keeping the lens from being huge and expensive.
The 28-135mm is a decent 'walk around' lens, although on a camera with an APS-C sized sensor, I'd prefer something like the EF-S 17-85mm. Its basically the same lens, just wider and in EF-S format for these cameras. Either way, the trouble with the lens is the limited maximum aperture of F4-5.6.
Something like the EF-S 17-55mm F2.8 IS, would be a better option...but costs a lot more.
Alright now I am confused! I like the 28-135 but am afraid the image will not be sharp enough. I also like the Canon 85mm f/1.8 or the Canon 50mm 1.4 or 1.8 for the better picture quality. Anymore suggestions??? THANK YOU!!!