Well, I can't say all Judo matches end up being won on the ground. But a lot do.
I don't think that it detracts from Judo. A good school should teach you a) good Ne Waza and b) condition you properly for a good long match or randori situation, whether it be on the ground or standing up. You aren't conditioned to stop when you are on the ground for a certain time. It's just that Judo likes to keep the action going.
Like I said in your other thread re Judo rules, Judoka have handled themselves very well against all grapplers, and the reverse is true. I know the guys who have practiced with Judoka on the MMA/Grappling forums have massive respect for them, and they seem to give as good as they get!
By the by, a thread by someone you might know. Grapplers here seem to think highly of ne waza: http://www.fightingarts.com/ubbthreads/s...ue#Post15852688
In conclusion, Judo has more than enough to help you become a good grappler. As you will know, it's all how you train. If you want to work a lot on your own Ne Waza, as your sensei. A good place to start is Katame no Kata. Practice that along with your other judo training.
I know many judoka who are "ground guys" and will try and take you down ASAP and choke you out. It suits some Judoka more. If it is something you want to do (i.e. a lot of ground work) talk to your sensei.
I would say Judo could live with any grappling style, Sambo or otherwise, on the ground. The breaking up of Judo players does not adversely affect their abilities as grapplers IMHO. You know the techniques, and Judo will condition you to go on as long as it takes.
P.S. The most spectacular thing in Judo is to see an Ippon throw. It is the "money shot", so to speak, hence the large amount of clips on the net of throws. Seeing a judoka hold another in hon-kesa-gatame for 25 seconds isn't just as impressive to the untrained eye!
Check out some comps to get a broader view.