http://www.livestrong.com/article/449125-how-much-actual-playtime-occurs-in-a-baseball-game/
According to this article, 2 games were timed for actual time the ball was in play. They included the time from the ball leaving the pitchers hand to the catcher and on balls that were hit, the time until the player was called safe or out. The two games, which were from different eras and timed by different people, came up with 8.5 minutes and about 12.3 minutes of time in play.
Baseball is obviously a different animal from football because you can ignore what happens in between whistles in football and still have an almost complete understanding of the game, whereas you can't say the same if you only viewed a baseball game from the time the ball left the pitchers hand to when the catcher caught it or a player was called safe/out. That being said, it does highlight one of the characteristics of the sport that can be polarizing, the action/waiting ratio. It comes down to personal preference of course whether you mind the increase in non-essential waiting time. For myself, as much as I love the game, I have a hard time spending an entire hour, let alone 3 during a weeknight. Even on weekends I can't spend the time to watch a whole game without liberal use of the fast-forward button on the DVR. When I'm at a game, I'm focused on the game for the most part, not socializing or playing with my phone, so I wan't the play to flow quickly. I'd welcome a pitch clock, reduction in mound visits, and requiring the batter to stay in the box and be prepared to take the next pitch. Tighten up the waiting time and I'd watch more and probably go to more games.