First, lets separate the two and talk about guitar. Sadly, even if you can rock it out on expert on the latest guitar hero, it probably won't help you out very much in the real guitar world. Pushing buttons just isn't the same as having to learn to press down strings. But there are some benefits. It will help you with dual hand coordination. Translation: It may be easier for you to fret a note with your left hand and pick a note with your right hand if you've had some Guitar Hero experience. Depending on the song and your right hand technique (all downstrokes or moving the controller down and up) it may even help with developing more solid rhythm or alternate/sweep picking. So, if I had to rate Guitar Hero's ability to prepare you for the world of actual guitar I would give it about a 3/10, only slightly higher than air guitar.
Now we come to drums. Caveat: I must first admit that I have only had limited experience playing with the drums on Rock Band and haven't had the opportunity to try it on Guitar Hero. That being said, I think that drums on Guitar Hero/Rock band are an adequate preparatory tool for learning drum set. You get the feel of holding sticks and playing with multiple limbs (both hands and your right foot) and it definitely helps with developing a solid rhythmic foundation. While playing drums on Rock Band I had to stop midway through the song and refocus because I caught myself jamming along to the song and playing parts that may not have necessarily been flashing on the screen. The Rock Band drum parts are a very decent replication of what it would feel like to actually play drums. It also gives a feel for staying in a consistent tempo (speed) instead of randomly beating drums in whatever tempo the aspiring drummer may choose. Now for the negative. Although Guitar Hero/Rock Band is a great way to get a feel for drums, it is almost inevitable that bad technique will form that will later have to be broken. Live drums feel and sound different then rubber pads (and are positioned differently), so this will take some adjustment. There is also no Guitar Hero/Rockband provision for your hihat (left foot) technique. But more important is stick grip and hand technique. The "caveman approach" to drumming (manhandling the stick like a club) that Guitar Hero/Rock Band often causes is quite different from the grips and finesse used in modern drumming. To be fair, most students begin drums with this caveman grip whether they have played Guitar Hero/Rock Band or not. Guitar Hero/Rock Band only strengthens a bad technique through repeated exposure. So, if I had to rate Guitar Hero's ability to prepare you for the world of actual drumming I would give it about a 7/10, a noticeable improvement from banging on mom's pots and pans in the kitchen.
It is almost funny to me how many beginner students I have that brag about the level that they can play on Guitar Hero/Rock Band and assume that they will immediately be able to transfer that over to the actual instrument. I think that speaks to our instant gratification culture, but I'll save that for a later blog.
In closing, here are two guys jamming out to arguably the most difficult song on Guitar Hero. Could these guys play this on real instruments? Not sure, but i'm impressed at their video game virtuosity: