Bowling wise Murali is pretty far ahead of everyone else. 556 @ 20.24
Closest competitor would be McGrath who took 297 @ 20.53 and thats a difference of about 259 wickets.
Best Bowler: Murali
2nd: McGrath
3rd: Warne
The batting competition is a bit closer than that with Ponting and Kallis.
Those two are a fair bit ahead of everyone else for me. The battle for 3rd is a bit tighter. With Yousuf, Chanderpaul and Lara all having a good case. After I removed Bangers and Zim from the records, Yousuf's average dropped from 60 to 55.68. Chanderpaul with 500 more runs than Yousuf and a fifth of a run less an innings (but a far superior runs per innings) gets the nod from me.
Best: Ponting 9253 @ 59.31
2nd: Kallis 8428 @ 58.93
3rd: Chanderpaul 6342 @ 53.29
But hey cricket isn't all about Tests! What about ODI's!?
3 names stand out in the bowling: Murali, McGrath and..... Pollock.
Best: Murali 335 @ 20.55 Economy 3.74
2nd: McGrath 234 @ 20.28 Economy 3.78
3rd: Pollock 275 @ 24.98 Economy 3.62
For the batting there is a fair bit of competition, with Tendulkar, Dhoni, Kallis, Ponting, Hayden, Hussey and Chanderpaul all leaving their mark on the decade.
Would personally go with
Best: Tendulkar 8530 @ 45.87 SR 85
2nd: Ponting 8922 @ 44.16 SR 85
3rd: Dhoni/Hayden Dhoni- 4827 @ 50.28 SR 91 Hayden- 5847 @ 45.32 SR 81
Murali dominanated the bowling, with McGrath being his only real competition in both forms of the game. Kallis and Ponting went pretty neck and neck in the batting, but there were a fair few that were there and thereabouts in the batting.
Kallis and Ponting were almost equally good with the bat at the top, but Tendulkar, MoYo, Hayden and Chanderpaul were also very close to the top as well. If we combine all 3 forms of the game played in this decade and look at these 6 players averages we will see how close they are together:
Kallis 16487 @ 52
Ponting 18576 @ 49.93
Tendulkar 15292 @ 48.70
MoYo 14592 @ 48.31
Hayden 14519 @ 49.55
Chanderpaul 12258 @ 47.88
That is a wwwwhoooole lotta runs, and in essence the 2000s have been all about the runs, but that just makes the top bowlers look all the more impressive. Their combined figures of all forms of the game see far less players rise to the top.
Murali 902 @ 20.35
McGrath 536 @ 20.38
Pollock 550 @ 24.76
Warne 438 @ 25.98
So the greatest cricketer of the decade leaves you the names of Ponting, Kallis, Murali, McGrath, Tendulkar, Pollock, Warne, MoYo, Chanderpaul and Hayden. But you go beyond the figures I've shown and you see more about the impact of the cricketers.
Ponting captained 2 Ashes losses in England, he also captained Australia to supreme dominance and world cup and champions trophy victories.
Kallis bowls! You wouldn't think it from what I've shown you but he's taken hundreds of wickets as well as been arguably the best batsman.
Murali bowled in an era of flat pitches and was only ever with one top class bowler at his side (Vaas) through the decade.
Tendulkar had all the weight of India on his shoulders, a pressure that is pretty much beyond anything most cricket fans can even begin to fathom, myself included.
McGrath had even less to work from with the pitches than Murali and had one of the most lucrative careers for a pace bowler in the history of the game.
Can't really put my finger on it personally.
Any of Tendulkar, Ponting, Kallis, McGrath and Murali could deserve the top placing. I think one of the most important things to consider is that the question says cricketer as opposed to player. This could suggest who was the best spokesmen for the game internationally, the best example of what the game is and means to the rest of the world?
Because of this I think I'll finally cast my vote on Sachin Tendulkar, but my feelings could be subject to change. There are plenty of deserving cricketers as I hope I've shown, but the Little Master's impact upon the game was an immensely significant on cricket in the 2000's.