This is a tricky list for me, because McKellen is one of those actors who seems like he's been around forever and done everything, but is mostly just known for 2 performances which span a total of 10 films. So, for these redundant performances, I will only be including one from each series - the one that stands out most to me as his best performance as that character. Additionally, he is also,very well-known for his Shakespearian acting, but I can honestly say I don't have much of an interest in those adaptations, as unfair as that may seem. So don't expect to see any on this list. Okay, disclaimers aside, now it's time for the list.
10. The Da Vinci Code 
Okay, this is not a good movie. It doesn't take a genius to know that, but during the scenes with McKellen, it's sometimes hard to remember that. He's an actor with such great presence and a Midas touch for making bad movies less bad. Who cares if the movie around him is stupid? He does a great job here and almost makes the movie work because of it.
9. Rasputin, Dark Servant Of Destiny 
Not the first movie out there to be totally stolen away by Alan Rickman (just wait, his list is coming soon), but somehow McKellen is able to get a few strong scenes in there. Even though his accent is a little...fuzzy.
8. Last Action Hero 
More than probably any other performance of his career, this role is more reliant on the actor's sheer presence than on any other aspect of his acting. Taking on the role of Death brought to life from the Bergman film The Seventh Seal is by no means a small task, even in a silly comedy, but he does it, and is actually pretty damn intimidating.
7. Cold Comfort Farm 
A somewhat bizarre role for the thespian (yeah, I use fancy words on this here interweb blog), McKellen plays a good old-fashioned fire and brimstone spewing preacher. But as strange of casting it is, he is the best thing to be found in this movie by no insignificant margin. He's the only thing about this movie that actually feels alive.
6. Mr. Holmes 
By no stretch of the imagination, this is one of the most no-brainer casting choices of the past several years. The fact that he hasn't played Sherlock Holmes before this is kind of miraculous, but being the fantastic actor he is, he brings Holmes to life in a way that few others have done before, showing him as an old man with a bad memory as well as tackling the emotional side of this generally one-note character (Mitchell And Webb have done it before, but it's not quite the same).
5. Richard III 
Okay, so I know I said I wasn't going into all the Shakespearian stuff at the beginning of this post, but, well, this list simply would not be complete without the inclusion of this fantastic film/performance. Richard III is generally portrayed in a simpler light than this, with actors often showcasing the warped and mutated side of the character, but instead of using his physicality as a crutch, McKellen utilizes it to help flesh out the role. Good stuff.
4. Apt Pupil 
A flawed film to say the least, this Brian Singer effort has several strong aspects, with the most obvious being the expert handling of one of its main roles by...well, this guy. Totally sinking into his character and making the German accent work, he takes what could have easily been a one-note role and transforms him into a complex and intriguing character that totally steals the show.
3. X2 
Remember when I mentioned the performances that span over several films? Yeah, this is obviously one of them. I felt his performance as the Holocaust-surviving Erik Lehnsherr (who later becomes the incredibly complex and powerful mutant known as Magneto) in the second X-Men film stands out the most, largely due to how well it showcases his subtleties more than just using his powers as the main attraction. Either way, he is always one of the best things about these films, and this one highlights that fact.
2. Gods And Monsters 
McKellen has made a lasting career of playing complex and damaged characters, and this one, more than the rest, shows off just how powerful and tragic he can be. As famed horror director James Whale, he delves into the intimate, emotional insecurities of the openly gay filmmaker in a way only Sir Ian could possibly manage. This is not to say his performance is totally humorless, as he handles the comedic side of this character just as well, making this a totally fleshed-out piece of nuanced acting. This should have won him an Oscar.
1. Lord Of The Rings: The Fellowship Of The Ring 
Ahh, Gandalf. One of the most beloved characters in the history of fantasy novels, and because of this magnificent performance, in the history of film. At his most raw and powerful, he takes this role and runs with it, taking what is already my favorite film in the series and making it all the more better. Not to say he wasn't also great in the following LOTR films, or even The Hobbit trilogy, but it was the freshness and intensity of his performance in the first installment of the film series that really stuck with me most. He's wise, entertaining, strong, and totally badass. Just take his scenes in the mines of Moria alone, between the inspiring, poetic speech he gives to Frodo, to his unforgettable showdown with the Balrog. This is a performance that cuts deep into the heart of the films and gives you an incredible character to root for and idolize. As a kid, and now as an adult, my thoughts have not changed; Gandalf is awesome, but McKellen is even more awesome for bringing him to life so convincingly.