The best replacement for wireshark is ethereal.

The best alternatives to wireshark are rated as following:
★★★★★  ethereal
★★★★  tcpdump
★★  snort
★★  charles
★★  fiddler
★★  microsoft network monitor
★★  omnipeek
★★  nmap
★  tshark
★  ettercap
★  commview
★  netmon
★  kismet
★  cain and abel
★  network monitor
★  burp
  firesheep
  netstumbler
  microsoft message analyzer
  ntop
  winpcap
  netflow
  windump
  wpe

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

Other search terms related to wireshark and their ratings are:
★★★★★ winpcap
★★★★ airpcap
★★★ gns3
★★ xquartz
★★ packet tracer
★ tcpdump
★ port mirroring
★ pcap
★ aircrack
You have in mind a companion for wireshark and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of wireshark in all years. Click on graph for more.
wireshark
ethereal
tcpdump