The "best" pet lizard generally is probably a crested gecko. Easiest care of any lizards I've kept, and among the hardest to cause permanent damage to. Interactive and easy to get along with, and cheap to feed and house.
Green iguanas are terrible pet lizards. YR is on the right track with enclosure needs, but add in some of the same sorts of handling issues I suppose some of the giant snakes have, and top it off with nutritional and UVB complications that no giant snakes have and that's an iguana. They should be an animal you have to know a guy who knows a guy to get a hold of one.
My fave lately are viper geckos. Relatively bulletproof, simple care and a lot more personality and handleability than their size lets on.
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