I agree that most modern lenses are pretty damn good, although you can definitely see the differences between the everyday lenses and the super expensive pro glass, especially in the long telephoto lenses. All of the top manufacturers make some fantastic lenses, but to be honest, for the vast majority of photographers (me included), the lenses are not the biggest factor limiting the quality of their photographs.
I shoot a Nikon D7200, which has an APS-C (i.e., not a full frame) sensor.
One of my favorite lenses is the Nikon AF 16-80mm f 2.8-4.0E VR lens. I think it's easily the best walking-around lenses for this camera. It's pretty fast for a zoom, getting 2.8 at the wide end and 4.0 at the long end. It gets great reviews for sharpness, and I've had no complaints at all with the image quality of my copy. What I really like about it, though, especially as someone who takes quite a lot of wider shots, is the extra 2mm at the short end of the lens.
Most of Nikon's standard APS-C zooms start at 18mm (equivalent of 27mm on full frame), and the extra 2mm gives me the equivalent of 24mm, which can be really handy. Sure, it doesn't have the range of the 18-140 or the 18-200, but for me the extra width (and wider aperture) generally more than makes up for the loss of telephoto range. I have a Tokina 12-28mm f 4.0, which I carry if I want some serious width, but the 16-80 is awesome for general use. It's a bit expensive new (close to $1,100 here in the US), but I got an immaculate used version for about half that, and have never regretted the purchase.
One type of lens that I find seriously impressive is the newer Nikon Phase Fresnel telephoto lenses. They've released a 300/f4E PF and a 500/f5.6E PF. The phase fresnel elements in these lenses make them incredibly small and light for their range. I've handled the 300/4, and it feels like a fake lens it's so light. It is just a little bit over half the weight of my older 300/f4 D Nikon lens, and less than three-quarters as long, but takes absolutely incredible pictures. The 500/f5.6 weighs less than half of Nikon's 500/f4E lens, and costs one-third as much, while delivering images that are basically as good. Both are out of my budget, though, at $2,000 for the 300, and $3,600 for the 500.
One of my favorite lenses is my older Nikon macro lens, an AF Micro 105mm f2.8D. The image quality is amazing, and the 1:1 macro ability is awesome. I've thought about upgrading to the newer VR macro lens, which gets fantastic reviews, but almost all of my macro shots are taken from a tripod anyway, so at the moment I really don't see the need.
