Scully-
Amount of runs scored in # of games played is a banal comparison at best, fit for people with a very crude understanding of cricket....like the average american for example.
There are several factors that influences runs/tests, many of which are out of a batsman's control.
For one, if you play in a weak team, you are forced to bat twice in a test match far more often than if you were in a stronger team ( contrast WI of recent years to that of 20 years ago for my point).
As such, an individual batsman has very little control if he can bat again and batting twice increases the probability of increasing your runs/tests ratio significantly.
Ie, someone scoring 60 and 40 in one match has a higher runs/test ratio than somene who's scored 80 & DNB in one match.
For two, your batting position is of consequence too, along with the strength of your team.
if you bat lower down the order, often enough you find yourself stranded at 20 not out or 70 not out and the match is over. A batsman higher up the order has more time and higher target to chase when he comes to the wicket.
You simply cannot ignore these factors.
As per your Greg Chappell vs Brian Lara goes, it is difficult to compare cross-era wise, but i hold Lara to be marginally better than Greg Chappell.
He's scored more runs against an attack of comparable strength and he's been the mainstay in a very weak batting lineup.
Plus Chappell cannot match Lara's stupendous appetite for humongous scores.
In terms of batsmen alltime, i rate the top 10 in the following order:
1. Bradman
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2. Viv
3. Sachin
4. Gavaskar
5. Sobers
6. Lara
7. Greg Chappell
8. Len Hutton
9. Neil Harvey
10. Rahul Dravid
And incase you wanna broach the subject of bowlers in the future, the following is my top 10 alltime pacer and spinner lineups:
Pace:
1. Malcolm Marshall
2. Denis Lillee
3. Imran Khan
4. Curtley Ambrose
5. Richard Hadlee
6. Glenn McGrath
7. Wasim Akram
8. Fred Trueman
9. Michael Holding
10. Sid Barnes.
Spinners:
1. Muralitharan
2. Warne
3. Subhash Gupte
4. Clarie Grimmett
5. Bishen Bedi
6. Bill O'Reiley
7. Chandrasekhar
8. Lance Gibbs
9. Jim Laker
10. Anil Kumble