Walking with Dinosaurs
Bringing back Jurassic era dinosaurs is a different story altogether. They have been dead for such a long time that their DNA will be too far degraded. Before looking at the very faint, almost invisible slither of a chance that science could bring them kicking, screaming and biting their way into the 21st century, let's examine all the reasons that would make such a scenario impossible.
In Jurassic Park, the book and movie, scientists were able to recreate dinos from DNA found in the blood of a mosquito that sucked on the giant beasts and then became preserved in amber. Although the dino DNA had been degraded over time, the gaps were filled in by frog DNA.
The first major problem with this scenario is that DNA is not a stable enough molecule, well not that stable that it will survive intact for millions of years. Too much important genetic information would be lost, even in a good preservative medium such as amber. Then there comes the problem of extraction and contamination. Insect and dino DNA would be intermingled and extremely difficult to tease apart. If any sequences were extracted there's always the potential for the lab to inadvertently sequence the DNA of a technician whose DNA could contaminate the ancient biological specimens. If dino DNA was able to be sequenced the gaps would have to be filled in by too much DNA from an extant species - such that any dino traits would be invisible.
Even if you were able to extract some DNA, there's no way of knowing how it was packaged into chromosomes, well not at the moment anyway. But let's suppose that some 'viable' DNA is found and packaged together, you will need an egg to get the whole show on the road. But which species of bird or reptile? They would have to be compatible.