Our son at age 6-9 really enjoyed Poptropica (www.poptropica.com), which has some fight competitions in it, however mostly involves solving puzzles to collect objects. Now (age 10), he's very into Roblox (www.roblox.com), which has lots of games designed by participants. It's Lego based, actually, so he might like that particularly. Some are obstacle courses, some are just situation/interaction, some are fighting/battle games. Both are free online sites with the option for 'membership' that gives perqs, but isn't necessary for kids to participate and have fun. Good luck... we restrict screen time to 2 hours a day on weekends, nothing on school days/nights.