Why he should be cast: A movie icon. Very obvious casting and a fan favorite.
Why he should not get cast: At 92, he may be a little too old for the role, and for sequels the role may need to be recast.
Conclusion: Due to his age, and the fact he already did a wizard character in the Harry Potter movies, I doubt New Line will give him serious consideration.
(Update: Christopher Lee passed away on June 7, 2015.)
Why he should be cast: Like Lee, a very obvious choice and a movie icon.
Why he should not get cast: At 85, he's younger than Lee, but still may be too old to hold the role for a franchise.
Conclusion: Considering he has been cast in the next "Star Wars" movie, he may be unavailable.
Why he should get cast: He's the right age, has the look, and is talented.
Why he should not get cast: No real reason.
Conclusion: Definitely a strong contender.
Christopher LloydWhy he should be cast: He looks the part, a great actor, and would be a very unique choice. He has also appeared in more comic book/comic strip/cartoon based movies than any other actor.
Why he should not get cast: Might make Shazam a little too quirky.
Conclusion: In just the last few days, a lot of buzz has begun swarming around him. He just might be the one to keep an eye on.
Why he should be cast: An outside of the box choice, even more so than Lloyd. A brilliant actor who would have an amazing take on the character. Just imagine Shazam with those Keaton eyebrows.
Why he should not get cast: At the end of the day, he's Batman.
Conclusion: Without a doubt an off beat choice that could pay off big. I see Keaton and Lloyd linked. If New Line decides to go in this direction, I think they will offer it to one, and if he refuses, they will go to the other.
(UPDATE: Keaton has defected to the MCU, in Spider-Man: Homecoming, making it highly unlikely he will be available for Shazam.)
Why he should get cast: a TV icon who would give the role dignity and heart.
Why he should not get cast: he may feel doing a superhero movie is beneath him.
Conclusion: Personally, I want Alda to play Grampa Freeman, but I could see him as Shazam just as well.
Why he should be cast: Perfect for the role. A movie icon and actually Egyptian.
Why he should not get cast: His age, 82, may play a factor, though not to the extent of the elder Lee and von Syndow.
Conclusion: The best actor for the role, but will his age hurt his chances?
(Update: Omar Sharif passed away on July 10, 2015.)