Anderson "The Spider" Silva - Unstoppable?

Yeah, we've heard that before. In the world of MMA, Champions don't usually stay champions for long. There's no feeding a fighter a steady dose of sub par competition to pad his stats, no lopsided matchups like a 9-0 fighter vs. a 2-8 guy. There's no 40-0 fighters in MMA. Competition at the top is insanely fierce, and with the vast array of ways fights can be fought and won, the titles change hands relatively often. Look no further than the current UFC Heavyweight Champion- Junior Dos Santos. He just won that title by beating Cain Velasquez on November 12th, in Cain's first title defense after beating Brock Lesnar. Brock actually defended the title twice before losing to Cain, after winning the title from Randy Couture. Randy only had one successful defense, when he beat Gabriel Gonzaga. All of this since March 3rd, 2007!
I remember when Lyoto Machida knocked out Rashad Evans (one of the best moments of my MMA fandom life) at UFC 98. I remember Joe Rogan exclaiming "This is the beginning of the Machida era, folks". In Machida's first title defense against Mauricio "Shogun" Rua, the two battled to a 5 round decision, which Machida took, 48-47 on all three of the judges' cards. It was a successful title defense, but holes were shot in Lyoto's invincibility for the first time in the UFC. I, along with many others, thought that Shogun had done enough to win the fight. Luckily for all fans, the UFC decided to put them together for an immediate rematch- Shogun knocked Machida out with a Knockout of the Night bonus to boot. Now Rua looked unstoppable! He just beat the everliving shit out of the elusive and highly regarded Lyoto Machida. How could he lose anytime soon? Well, Shogun's first title defense was against Jon "Bones" Jones. Jones TKO'd Shogun in the 3rd round to win the UFC Light Heavyweight title. That was just this March! Jones has since successfully defended the title once, against Quinton "Rampage" Jackson. Now, everyone is calling Jon Jones the new, unstoppable UFC Light Heavyweight champ.
Current UFC Middleweight Champion Anderson "The Spider" Silva has the longest all-time UFC title reign, at 9 successful defenses in a row. He is the current pound-for-pound #1 fighter in the world, and likely the best fighter in MMA history. During this current reign, Anderson has twice gone up in weight from his normal 185 to 205 to fight. The first was against James Irvin, a middle-of-the-road Light Heavyweight. Anderson knocked Irvin out in 1:01 of the first round. The second was against Forrest Griffin, a former UFC Light Heavyweight Champion. Anderson knocked Griffin down 3 times before knocking him out with a jab while literally walking backwards- all in the first round. For that performance, Anderson won both Fight of the Night and Knockout of the Night, along with the $60,000 bonuses each award came with. His records are absolutely absurd: A perfect 1.000 winning percentage in the UFC. Most UFC title defenses at 9, longest all time UFC win streak at 14, most all time knockdowns in UFC history with 15, and the longest title reign in UFC history. Aside from his fight with Chael Sonnen, Anderson has even looked unbeatable when his fights were taking place. If any reader has seen the fight between Anderson and Demian Maia, as agonizing as it was, it just highlighted the gap in MMA skill between the two fighters at the time. With little time left in his career, can Anderson Silva be beaten? Will he retire as UFC Middleweight Champion, and the best fighter of all time?
Probably. As much as I hate to say it, probably. Who do you think can/will beat him?

Here's a video with some Silva highlights. From :38 seconds to :47 seconds it shows the knockout of Forrest Griffin I was referring to. It's ridiculous.