The unfortunate reality of photographing lions is that you're going to want to have layers of fence and/or plexiglass separating you from these Great Cats that see just one thing when they look at you: lunch.
Here's a little anecdote from my visit to the Lion Habitat in Henderson, NV, home of the MGM Grand's two lions along with 20 or 30 others. The MGM lions are the first kitties you see when you walk into the habitat. Most of their living area is surrounded by a high, double-layered fence, but there's one spot that's just a sheet of thick plexiglass. There's a raised platform on the lions' side that the trainer can toss bits of food onto, so visitors can get a good look. One of the big fellas leapt up onto the platform while we were standing there next to a family with two small children. And that lion, bless him, suddenly lunged straight at the smaller of the two kids, mouth open.
Good job, protective plexiglass.
I did my best to make these photos presentable, but it's impossible to completely edit out the fact that there is always a barrier of some sort between the lions and their visitors. I'm still pretty happy with how the photos turned out. And hey, no one got eaten during my viisit.