The random system they use now is the way to go. After having played Halo with both Veto and Voting, this is the best system.
As someone else pointed out, voting just leads to the same few things getting played over and over and over and over again. The veto system is better than voting. But, veto still leads to idiots screaming into their mic, "Veto, veto, veto this! Come on guys, veto this!", and then they get mad and frustrated when not enough people veto. Both systems lead to people getting mad when not enough of the other players agree with their vote/choice to veto. That's why the random choice is the best. Nobody can get mad at the other players over the map/gametype because player choice was taken out of the equation.