Yeah, This was a bit botched
Tim Schaeffer is a highly-regarded game developer whose games haven't sold shit in years. Psychonauts was an excellent game that bombed unbelievably poorly. With Jack Black providing the lead voice and a wide array of cameos from legends of heavy metal (it's the most coherent Ozzy Osbourne has been in decades now), Brutal Legend hopes to give Schaeffer some commercial viability in addition to his usual quality.
So, how does it do?
Honestly, it's a very mixed bag.
In the game, you are roadie Eddie Riggs, who is transported to the heavy metal world and help to fight the emperor who was oppressing them. It is a wide open world with tons of things to do --- but that is one of the first problems. There is too much stuff to do and it makes doing anything but the main story just a pointless grind. You can do racing minigames which are exceptionally unenjoyable. You can help your friends ambush people and they are probably the most enjoyable distraction, but they aren't that great. You can find all of the assorted relics, legends, and serpents hidden all over the world, but again, it feels like a Rare collect-a-thon and that is a gameplay style that has not aged all that well.
The main game storyline is legitimately enjoyable. The storyline is simultaneously funny and kick-ass. The missions have a fun mix of play styles...with one notable exception that you deal with frequently and never is fun.
BL contains a fairly poor RTS game that you have to play frequently. Admittedly, I'm rather bad at RTS as is, but the controls are highly clunky. It is simply a chore to play and very much not-fun to play. And you do them frequently, which is hardly enjoyable.
BL tries to do a great many things and does most of them well, but nothing is truly outstanding. Nothing is truly great. Everything has little problems that overall hurt the experience. Which is a shame, because this did look like the game that would give Schaeffer the commercial viability his usually outstanding work warrants. But this time, his design just didn't hold up.