What if the 1965 Packers met the 1985 Bears? Or the 1927 Yankees faced off with the 1975 Reds? A great online tool lets you simulate those matchups. At the What If Sports website, you can create a sim matchup for any NBA, NFL, NHL, or MLB teams, plus a large number of college basketball teams. The engine behind this seems to be pretty robust. It doesn’t just generate a final score but a complete play-by-play account of the game, and of course box scores and statistics. Single games are free, or if you’re more hardcore you can join a simulation league.