You have the Canon EF-S 18-135mm f/3.5-5.6 IS USM Lens. Right? Actually this is a pretty nice inexpensive lens. The zoom range is too long for my liking but it dose a satisfactory job for a GP lens.
You are going to have to do two things to get a really better lens. One is settle for less zoom range and drop more coin on more expensive lens. Zoom range and quality usually go in opposite directions. People that want large zoom ability are more interested in snap shots. People that want the best in IQ settle for shorter zooms.
IMHO, the sharpest and best lens in this category is the Sigma 18-35mm f/1.8 DC HSM Art Lens for Canon. But you notice it doesn't have the range your current lens does. Plus it is around $800 bucks.
Tamron has the Tamron 16-300mm f/3.5-6.3 Di II VC PZD MACRO Lens for Canon. Huge zoom range. If it can't do the trick in a all-in-one package nothing can. I think they are around $600.
Canon has the EF-S 55-250mm f/4-5.6 IS STM. It is a really nice, really sharp zoom. A good buy at three bills. Canon also has the EF-S 18-200mm f/3.5-5.6 IS which I am not a fan of at all.
A little known but one I really like is the EF 28-135mm f/3.5-5.6 IS USM. Been around forever but a real jewel. I have one of these, actually several !
But if I were buying one today the one I would buy is the EF-S 17-55mm f/2.8 IS USM. Costs a bit more but man this one is fantastic. Second choice would be the fast Siggy above.
EB
EOS 1D, EOS 1D MK IIn, EOS 1D MK III, EOS 1Ds MK III, EOS 1D MK IV and EOS 1DX and many lenses.
