@
HostileOSL - seriously dude putting a credit cost on a link to an article you most likely Googled, not nice behaviour...
Back to the topic, depends if the price difference is worth it for the performance increase (17% on benchmarks base 2080 vs 1080 but real life will be less and to be honest at that level will you want to settle for the base model), the RTX is newer (also still at the start of the dev cycle) so should have a longer usable life but again if you are prepared to spend that type of cash on one card then I'd expect you to be upgrading on a regular basis anyway.
The RTX is the successor to the GTX so newer games may support the newer features but the GTX will still be well supported for the next few years as it is still at the top end.
Last but not least, if the rest of the machine isn't optimised then your just throwing money away as it's not going to perform well anyway.
FYI I currently have a Gigabyte G1 1060 & an EVGA 950 SSC and NEVER came across anything I can't run at highest detail at a good frame rate, they run well together and the fact that the rest of the machine is a bit of a beast does help lots.
I'd have to say if you have the cash and want to keep the card for no more than 2 years and would like to upgrade another component at the same time get the GTX, if your intending sticking with it for 3 years and don't need any other upgrades get the RTX :)