How do you do it in defining as somebody as a true great of cricket (ie Shane Warne, SRT, Sir Isaac Vivian Alexander Richards, Sir Garry Sobers etc.)? And in the real game of cricket, Tests. And I will give credit to SJS for giving me this idea in the Virender Sehwag thread.
For me as a general run down:
Consistentcy - always performs no matter what, sure they might have a slight dip in form (that would be almost impossible not to), but that is few and far in between the periods when they are on top of their game.
Technique - It may not be coached, but it must be good enough to either take a lot wickets (ie a good run up and action) or to be able to score a lot of runs. Somebbody with a shocking technique like Virender Sehwag can't be considered a great, because in my opinion having a bad technoqie can lead too your downfall whilst batting, or lack in consistentcy and therefore not score as many runs and be in and out of the team. Bearing in mind that being as technically correct as a Daren Ganga or Ramnaresh Sarwan (Camps to correct me in 5..4..3 ) isn't a surefire bet to being a legend of the game. It has a lot to do with the midnset and application of the individual.
Which brings me to the next point:
Mental - You must never be scared or defeated. Look at Shane Warne, many a batsman as got the better of him (Brian Lara in 1999, VVS Laxman in 2001), but he is never defeated mentally. I can't think of too many times for example that SRT was defeated mentally by the Australians. And this is also under the banner of being able to perform when the going gets tough and is able to raise above it.
Genius - Something no mere mortal or standard Test cricketer could do. Just watch at how Warne or BCL batted or McGrath bowled, I could practise either one of leg spin, batting or fast bowling for every day till the cows come home, and still no do anything extraordinary
I'll add more as I see it, but this is just a general run down of it all and what I could think of at this time being.