A better way to list users currently logged on

We can use,

Tcode: 

SM04 - for Active users on one application server.

AL08 - for Active users on all application servers logged in globally.

Report :

CCUINIT to initialise measurement of concurrent users.
CCUEVAL to get the output of report CCUINIT.
Please note that CCUEVAL is not be relied only in case of HTTP users. If you do not have HTTP users then the report can be relied.