Analysis
Misty Terrain seems to be most useful, as it's essentially Safeguard with the added bonus of Dragon moves halved in power & Nature Power becoming Moonblast. However, most of the Pokemon that can learn it aren't meant to be set up Pokemon. Arguable exceptions are Mr. & Mrs. Mime, Mewostic (M) and Florges.
-Mr. Mime has better things to do like setting up Dual Screens, the same with Prankster Meowstic, though if you have enough Fairy types on the field then I guess it's worthwhile.
-Florges has enough bulk, but it has much better support moves like Aromatherapy and Wish to make use of (unless this is doubles/ triples, in which case Wish is not as useful).
Electric Terrain is something that I don't recommend. It only prevents the Pokemon on the ground from falling asleep, and while it does boost Electric moves by 50%, all the Pokemon that can use it are too frail to set up and have much more useful moves. Life Orb & Specs/ Band is more recommended, and the only Pokemon I can see using this move is Ampharos, since it can be used as a Dual Screener and therefore a set up Pokemon.
Grassy Terrain might be considerable for a stall team, since it basically grants grounded Pokemon a Leftovers and activates Grass Pelt, but that also applies to your opponent's team as well. Once again, most of the Pokemon that can use it are not bulky enough to set up or have better moves. Pokemon bulky enough to set up are Tangrowth and Florges, but again they have better moves to use.
Conclusion
The Safeguard effect of Misty Terrain is useful, and if you want Safeguard but are using Pokemon that can't learn the move, then it is a viable option, except that Flying & Levitating Pokemon are not eligible for the benefits of Misty Terrain.
Generally speaking, all three moves are not highly recommendable, as you have waste a turn to set up, and it affects your opponent's as well as your own Pokemon.
If you really want to use any of these moves, use them in doubles/ triples, because single battles see so much switching that you will likely need to switch to a Pokemon that won't benefit from the terrain moves.
