I should have been more specific by saying whether anything more than an mx518 (or something a little earlier before it came out) with 1600dpi sensor is easily surpassed by newer technologies which put gamers playing with those older equipment at a significant disadvantage.
Small non gaming travel mice wasn't the intent of my OP sorry.
I've used most of the iterations of Logitech mice based on the MX518, and can't really say that the tech has made them better for gaming. Here's my quick thoughts on the different ones I've owned.
MX518 - After having used early Razor mice (original Boomslang and Viper), I finally found the mouse that really works for me. I've tried newer Razers and different Logitech mice, but I keep coming back to this basic shape. I actually still use my first MX518 at work.
G5 - Really appreciated the addition if the tilt wheel. I use the left tilt for melee and right tilt for crouch toggle in fps games. For some reason they removed one of the left thumb buttons in exchange for tilt wheel.
G5 (second one) - Logitech replaced my original G5 because the finish had come off the original one. I got a second revision which added the previously removed left thumb button back. This mouse was almost perfect IMO. However, the finish ended up wearing off of this one too, and I replaced it with a G500s.
G500s - same comfy shape, with three thumb buttons now. The shape of the thumb buttons took a while to get used too, since they are no longer rounded. I generally keep the DPI setting below 3200, so I am not using anywhere near its max of 8200. The best new feature is the on board profile storage. Your mouse keeps settings like DPI and any custom buttons stored, which is nice if you used it with a multiple computers or re-install your OS somewhat frequently.
Basically, the mice are still the same for the most part (which is a good thing IMO). They did bump up the DPI significantly over time, but I find that I don't really use it. The tilt wheel added more to the design for me in terms of gaming than increases in DPI.