First off injuries are a way of life in the NFL so you need contributions from all the first rounders you draft.
1) CB Mike Jenkins - At this point Jenkins is the #3 CB which in today's NFL means he's a starter behind Newman & Henry. Should AJones be reinstated & beat out Henry for starting job, we now have the option to move Henry around as needed. Jenkins will not doubt remain our #3 CB and don't forget the 09 season will be Henry's last year with the Cowboys unless we resign him. Presume you smart enough to want the Cowboys to have good depth at the important CB position if you want us to win postseason games. Besides, Newman is 30 and in reality Pacman (if he can stay clean) along with Jenkins & Scandrick are our future starters at CB with probably Ball giving us an excellent core of players. So no there's no way I'd give up this pick for any other player.
2. RB Felix Jones - In addition to bringing the burst of speed we lack in a RB, he'll also probably become a major contributor in our passing game. Figure him to get 10-15 snaps on the field combined as a WR/KR/RB cause I still don't see MBIII getting more then 22 carries. Since no team believed any of the 2008 WRs had #1 value, can't argue if Felix can take it to the house either as a RB or in various slots as a pass catching RB/WR. Hopefully long term he turn's into a player like Brian Westbrook of the Eagles.
3. Somewhat surprised you included Anthony Spencer in this short list since it very obvious (because Wade has said it) that we very much want to get Spencer on the field as often as possible. Everybody realizes (except you) that Spencer could very easily become our starting OLB before the end of the season and Ellis becomes much more of a situational pass rusher then an OLB. BTW: Ellis contract with the Cowboys ends after the 09 season.
4. OLB/ILB Bobby Carpenter - Now this guy is worth mentioning here. It's obvious he hasn't become the player Parcells and most of us hoped for. But we drafted him cause we didn't know that Ellis could make the transition to OLB which was prudent call at the time. Now, all we can hope for is that Carpenter continues to play very well on ST but as he now entering his 3rd season we all are justified in expecting more from him. It's not lost on most people that Carpenter is #3 on the depth chart at ILB behind Zack & Burnett & Justin Rogers has just been moved inside to backup the primary backup behind Bradie James. I like Carpenter but his future very shakey in Dallas. So in hindsight I'd sure like to have used this pick on best WR available whose now proven to be successful; but we all know Parcells wouldn't draft a WR in the first round. Got any ideas which WR we should have drafted who could be a big help now?
5. You mentined Spears but didn't include him on your list. He hasn't been a bust cause he's been our starting DE since we drafted him. He's good against the run but hasn't helped much at all as a pass rusher--which is why he faces criticism. Maybe Hatcher can beat Spears out as a pass rusher but not so sure he's anywhere near as good as Spears against the run & that's the first area of responsibility for a DE in the 34. For what it is worth, Spears looking real good in this morning's practice in which the Cowboys wearing pads/helmet. He's really getting through our OL and along with other defensive players bringing pressure on Romo & Johnson. So since Spears is still a starter & we've got no problem player behind him, which WR drafted later in the first round would you take over him?