The best replacement for xquartz is x11.

The best alternatives to xquartz are rated as following:
★★★★★  x11
★★  x11 mac
★  xcode

Your alternative for xquartz is not listed? Suggest!
Speaking about xquartz, one probably shouldn't forget about wireshark.

Other search terms related to xquartz and their ratings are:
★★★★★ wireshark
You have in mind a companion for xquartz and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of xquartz in all years. Click on graph for more.
xquartz
x11
x11 mac