I want to construct a Lan of game to play something like Starcraft,Redalert,Dutycall and so on between my neighbours.But the most concern is the Lan virus,does Mikrotik can deal with the Lan virus like drop all ethernet ports except individual ports which used to transmit the game data with eachother? And other computer virus is beyond of my concern if it isn't disabled the Lan network.

Question two:
I want to document the results or grades of the game or someone who quit the game in the midway. So can I know the results or credits or status of the game by intercept the ports which used to communicate the game data of each players?

you should install dedicated game server. for example, PvPGN. also there are bots for different games (like Ghost for DotA) which collects statistics on that server

and all that have nothing to do with RouterOS

I mean that whether if the Mikrotik can control or eliminate the spread of Lan virus through drop all ports except several game ports. Can this way avoid Lan virus' spread effectively? Thank you .
I most concern is the Lan virus spread.

well, viruses work via port 445 (Microsoft NetBIOS, RPC), so you can block that port (if you don't need filesharing via NetBIOS)

Or take a more secure whitelisting approach and build a firewall rule set that accepts connections on the ports necessary for the game to work, and drops everything else.

Most games can work with routed networks too.
That means you can put each user in a different subnet and only allow access to the subnet of the server and only the port of the gameserver.
That would minimize the possibility for viruses to
a) misconfiguration
b) errors in ROS
c) errors in the Gameserver software