So many aspect to consider
Panel Type: TN vs VA vs IPS
Panel Design: Straight vs Curved (1000R 15000R 18000R lol)
Refresh Rate: 100HZ vs 144HZ vs 165HZ vs 200HZ
Ratio: Wide 16:9 vs Ultra-Wide 21:9
Resolution: 1080p vs 1440p vs 4K (at lower refresh rates)
Display size: 24inch to 38inch
HDR: no HDR, HDR, HDR+, HDR10, Dolby Vision
adaptive Sync: G-Sync compatible, G-sync, G-Sync Ultimate, Freesync, Freesync 2
Everyone has different preferences. Just filter in a price search engine the features which are a must for you and there are a lot less monitors to choose from.
F.e. the last time I was searching for a monitor, i absolutely wanted more than 1080p, so I filtered away any 1080p-monitor and below.
Coming from a 120 Hz monitor I didn't want go back to 60 Hz or 75 Hz (100 Hz would have been the lowest acceptable). At that time there weren't any 4K monitors with more than 60 Hz available, so 4K was out... my GPU also was glad about that.
I'm no fan of ultra wide monitor since 95% of games are optimized to 16:9 aspect anyway.
I also absolutely wanted adaptive sync, compatible to my Nvidia GPU.
After these decisions there were only a few 2560x1440p G-Sync-monitors with 120 - 165 Hz to choose from. Two of them were on sale, the rest much more expensive.
So I bought one of the bargains (HP Omen 27, 2560x1440p, G-Sync, 165 Hz, only TN panel, no HDR) and I am still very happy with it.
Meanwhile I can switch between the HP Omen 27 and my LG C9 OLED TV, so if I want to play a slower game in 4K and HDR up to 60 Hz, I just change the video output. For 4K, HDR, 120 Hz, G-Sync compatible I have to wait for the new graphic cards with HDMI 2.1Last edited by Conina - on 16 June 2020