Tim Kitzrow, the original voice actor on NBA Jam, has been roped in by Valve to provide a commentary pack for DOTA 2.
So far I feel that you would have to go a long way to beat these three anouncer packs that can all be got pretty cheaply: Stanley Parable, GladOS, and Rick & Morty.
They are all so dynamic and feel so natural. Too many of the other anouncer packs feel like they are trying way too hard. Or are piloted by a really annoying voice. I wont touch that Meepo pack with a ten foot pole for this very reason.