Who Do You Think is the Best SciFi author (Novels) of the last 25 years and why do you think so?

Very difficult question because it's hard to narrow it down. I can only suggest a couple and say that I'm sure there are many many others who also are absolutely fantastic & great. So I would suggest Orson Scott Card (writes sci fi and fantasy) and Vernor Vinge. But I'd never limit it to just those two.

Im Sorry I should have specified I was wondering about authors affter the Big three (Asimov, Heinlein, & Clarke) and Deffinetly affter Verne.

Personaly I Am a Big fan of David Weber, who writes wonderful Military SciFi with engageing charaters but also interweaves all of society into his works. He can merge socio-politics, ecenomics, faith and military stategy into the tapestry with Great Characters and many different places and setings for the human experiance.

While I would have a hard time narrowing it down to only one, I will mention at least a few authors who I feel have earned the term "great" for their ability to present ideas that truly force the reader to think about them while still remembering the demands of a good story.

Orson Scott Card
Vernor Vinge
Nancy Kress
Eric Flint (very different from the other picks and only for some works)

Honorable Mentions to Connie Willis, Lois McMaster Bujold, Harry Turtledove, Neal Stephenson

I think Anne McCaffery, her Federation of Sentient Planets universe with all of the different series of book which expands it to it a universe with such detail to the individual stories makes her probably the best female scifi writer to me.

I would be torn between Robert Heinlein and Issac Asimov with Larry Niven following closely. Heinlein wrote the first SF book I read, "Red Planet" that sent my imagination soaring whereas when I got exhausted from reading all the Lord of the Ring Series, I picked up Foundation and found it addictive. Then when I discovered Ring World by Niven, it also really gave me vivid images of a far away world. However, there are only a couple of Ring World novels and Niven also writes fantasy books "The Magic Goes Away" so he comes in after the 2 masters (the 3rd is often referred to as Arthur C. Clarke but he's a bit too sophisticated for me.)

I would have to say Neal Stephenson.

He knows how to weave multiple storylines together masterfully, and can go into detail yet even when he is making stuff up, he does so in a manner that is so plausible that you can't help but believe it at least enough to say, "Man, this is good stuff!".