How to replace Brundle? Impossible. The only commentator that could be worse is James Allen. Anything is an improvement.
I was glad to find somebody equally unimpressed by the jabberings of Humphrey & Jordan, but Brundle? Waaat? 
Who's your idea of a good commentator?
Of course, it's all down to personal taste. I liked Martin Brundle, with his gridwalks, features and commentary. I also really enjoy the pundit-team that is Jake Humphrey, Eddie Jordan and David Coulthard... it's full of fun and good banter and has generally proved very popular with viewers.
In the days of Jonathan Legard, people seemed very much against the poor man... saying he made mistakes left right and centre and that he got too excited too quickly. Well, the same can be said of both James Allen and Murray Walker to be honest.... the issue is with the latter.... he did it for so long he became an icon (and rightly so, don't get me wrong!)
Like Legard, Walker muddled things up and made mistakes too (hence the nickname "Muddly Talker"). AND he also got seriously excited at the slightest thing. All this I loved, which is why I probably didn't mind Legard so much. James Allen on the other hand, while possessing all these flaws... was seriously biased towards certain drivers, especially Jenson Button, and that drove me up the wall no end....
Each to their own I suppose.