If you're talking about animals to compete in popularity with the commons (axis, fallow, sika, BB, aoudad, etc), ultimately price, trophy,'fit' for exotic ranches, and availability of founding stock is going to be the determining factor.

Price- There is much more of a market for $1500-2500 animals than $5-10K+ animals, you just have more hunters that can afford that range, and those that can afford more will still shoot 5 of the commons for every one of the supers. Plus, there are a lot more breeders who can play in that range. IMO, if some of the supers were half the price, you'd see a LOT more of them b/c ranches without breeding pens or multiple subdividsions would be more inclined to turn them loose.

Trophy - they have to have an impressive look horns/antlers/coloration, etc. without being so specialized that only the SCI crowd knows what they are. Fringe-eared or beisa oryx are a great example - to the average hunter, they look like a gemsbok - so why pay 2x the price? Hog deer or muntjac are others - cool critters, but the average joe hunter doesn't know what they are, and even if they did, may not value the premium paid for something that's not that impressive comparatively.

Fit - Basically, the popular exotics IMO are popular in part because they provide a challenging hunt. Some hunters don't care about this and just want to collect a critter, but most want a good experience, challenging chase, and to come home with a trophy. Some animals just don't fit well with our terrain, or don't fit well with the size and setup of most exotic ranches. Sitatunga and bongo for example are complete fish out of water here, and some species like sable (and bongo) are so rarely hunted that they become pretty tame. The 'fit' part also touches on size a bit - you can have a very challenging hunt for a 150lb sika on just about any ranch, but stick a 1500lb eland on a couple hundred acres, and not only will it tear up the browse, but won't be that challenging a hunt either.

Availability of founding stock - pretty self explanatory, but if you can't readily get new stock to refresh your genetics, then breeded interest will be low.

I would also like to see Ranches raise Bongos

You do see fallow more than you used to but they don't eat as well as axis imo. But they aren't the jumpers axis are so they seem to keep better with lower fences and I think that helps their popularity. What I hate is all the dang sheep and goats people are keeping now.

I think really hot nymphomaniacs are a good bet. Put a few of them on a ranch!

I got 3! Bout time we get some young'ns hitting the ground!

That's wonderful, are they a pain to keep in a fence?

A couple ranches in Nevada raise them, but they are damn expensive. You can't actually buy them, just rent.

Some of them are in movies!

Roo,
I've learned that sometimes it is better to rent. Lower total cost of enjoyment that way and you can trade in when you see a better model.

Love my wife, but won't do it again if she goes first. LOL