With the release of the final roster cuts heading into the 2010 season, I thought it would be a good time to look back at what, if any, improvement the Cowboys have achieved in the last four years. So I've made a table of the last four years of depth charts, including this one, and then assigned a simple 1-5 rating to each player for each year's performance.

• In all cases where a player went to the Pro Bowl, I chose not to argue with the fans, coaches, and players of the NFL, and assigned the highest rating for that player's season.
• For non-starters, the ratings are biased toward skill over performance. For instance, Jon Kitna had zero snaps in 2009, but was still an average QB.
• For starters, the ratings are biased toward performance over skill. For instance, Ken Hamlin had a huge dropoff in performance from '07 to '08.
• There are a lot of average players in the league. A lot of them aren't starters. If a player outshines a number of other teams' starters at his position, then he is at the very least an above average player.

EDIT: Below are all the changes I've made so far based on your feedback. I'll keep updating this list as you keep convincing me I'm wrong. :)

1. Michael Hamlin, 2008, 2 (accidentally omitted due to position confusion - I'm going with SS)
2. Barry Church, 2010, 2 -> 1
3. Danny McCray, 2010, 2 -> 1
4. Terrell Owens, 2008, 5 -> 4
5. Roy E. Williams, 2008, 2 (another accidental omission, mid-season trade)
6. Roy E. Williams, 2009-2010, 4 -> 3
7. Dez Bryant, 2010, 4 -> 3
8. Doug Free, 2009-2010, 3 -> 4
9. Stephen Hodge, 2009-2010, 2 -> 1
10. Sean Lee, 2010, 3 -> 2

EDIT: Leave it to OCC to point out some interesting statistics that make the storyline more compelling :) He summed up the stars for each year in a comment below. I'm going to take a slightly different approach in that I'll just sum up the stars for the top 53 guys for each year, including those on IR. This should help make it an apples-to-apples comparison as the number of players that were on our roster at some point varies year to year.

Legend
	Among the best at his position
	Above average
	Average
	Below average
	Among the worst at his position
	Did not play due to injury
(Bold)	Starter

Depth charts after the jump...

2007		2008		2009		2010
Quarterbacks
Tony Romo		Tony Romo		Tony Romo		Tony Romo
Brad Johnson		Brad Johnson		Jon Kitna		Jon Kitna
				Stephen McGee		Stephen McGee
Running Backs
Julius Jones		Marion Barber		Marion Barber		Felix Jones
Marion Barber		Felix Jones		Felix Jones		Marion Barber
Tyson Thompson		Tashard Choice		Tashard Choice		Tashard Choice
Fullbacks
Deon Anderson		Deon Anderson		Deon Anderson		Deon Anderson
Oliver Hoyte						Chris Gronkowski
Wide Receivers
Terrell Owens		Terrell Owens		Miles Austin		Miles Austin
Terry Glenn		Patrick Crayton		Roy Williams		Roy Williams
Patrick Crayton		Roy Williams		Patrick Crayton		Dez Bryant
Miles Austin		Miles Austin		Sam Hurd		Kevin Ogletree
Sam Hurd		Sam Hurd		Kevin Ogletree		Sam Hurd
Isaiah Stanback		Mike Jefferson
		Isaiah Stanback
Tight Ends
Jason Witten		Jason Witten		Jason Witten		Jason Witten
Anthony Fasano		Martellus Bennett		Martellus Bennett		Martellus Bennett
Tony Curtis		Tony Curtis		John Phillips		John Phillips
Offensive Tackles
Flozell Adams		Flozell Adams		Flozell Adams		Doug Free
Marc Columbo		Marc Columbo		Marc Columbo		Marc Columbo
Doug Free		Doug Free		Doug Free		Alex Barron
Pat McQuistan		Pat McQuistan		Robert Brewster		Robert Brewster
James Marten				Pat McQuistan		Sam Young
Guards
Leonard Davis		Leonard Davis		Leonard Davis		Leonard Davis
Kyle Kosier		Kyle Kosier		Kyle Kosier		Kyle Kosier
Cory Proctor		Montrae Holland		Montrae Holland		Montrae Holland
Joe Berger		Cory Proctor		Cory Proctor
		Joe Berger
Centers
Andre Gurode		Andre Gurode		Andre Gurode		Andre Gurode
[Cory Proctor, G]		[Cory Proctor, G]		[Cory Proctor, G]		[Kyle Kosier, G]
				Duke Preston		Phil Costa
Defensive Ends
Chris Canty		Chris Canty		Marcus Spears		Marcus Spears
Marcus Spears		Marcus Spears		Igor Olshansky		Igor Olshansky
Jason Hatcher		Jason Hatcher		Jason Hatcher		Jason Hatcher
Stephen Bowen		Stephen Bowen		Stephen Bowen		Stephen Bowen
						Sean Lissemore
Nose Tackles
Jay Ratliff		Jay Ratliff		Jay Ratliff		Jay Ratliff
Jason Ferguson		Tank Johnson		Junior Siavii		Josh Brent
Outside Linebackers
Demarcus Ware		Demarcus Ware		Demarcus Ware		Demarcus Ware
Greg Ellis		Greg Ellis		Anthony Spencer		Anthony Spencer
Anthony Spencer		Anthony Spencer		Victor Butler		Victor Butler
Justin Rogers		Justin Rogers		Brandon Williams		Brandon Williams
				Steve Octavien
				Curtis Johnson
Inside Linebackers
Bradie James		Bradie James		Bradie James		Bradie James
Akin Ayodele		Zach Thomas		Keith Brooking		Keith Brooking
Kevin Burnett		Kevin Burnett		Bobby Carpenter		Sean Lee
Bobby Carpenter		Bobby Carpenter		Jason Williams		Jason Williams
				Stephen Hodge		Leon Williams
						Stephen Hodge
Cornerbacks
Terence Newman		Terence Newman		Terence Newman		Terence Newman
Anthony Henry		Anthony Henry		Mike Jenkins		Mike Jenkins
Jacques Reeves		Mike Jenkins		Orlando Scandrick		Orlando Scandrick
Courtney Brown		Orlando Scandrick		[Alan Ball, FS]		[Alan Ball, FS]
Evan Oglesby		Adam Jones				[Akwasi Ansah, FS]
Nathan Jones		Alan Ball
Strong Safeties
Roy Williams		Roy Williams		G. Sensabaugh		G. Sensabaugh
Keith Davis		Pat Watkins		Pat Watkins		Michael Hamlin
		Keith Davis		Michael Hamlin		Barry Church
				Marvin White
Free Safeties
Ken Hamlin		Ken Hamlin		Ken Hamlin		Alan Ball
Pat Watkins		Courtney Brown		Alan Ball		Akwasi Ansah
						Danny McCray
Specialists
Nick Folk		Nick Folk		Nick Folk		David Buehler
Matt McBriar		Matt McBriar		Matt McBriar		Matt McBriar
L. P. Ladouceur		L. P. Ladouceur		L. P. Ladouceur		L. P. Ladouceur
				David Buehler