Judo makes a fine base for MMA but only IF you have trained it from an early age. The reason is simply because Judo techniques were not designed for MMA and have a huge learning curve, plus a transition to no-gi. Judo was meant as a sport for physical education, and that's really what you get out of it. You'll create some tough athletes with great coordination and reflexes, but they will have spent much of their effort on techniques not application to MMA.
So if you are looking into MMA, the answer really depends on your background. If you are an older striker who is looking for takedown defense and maybe one backup takedown, then wrestling is faster. If you are a grappler who is looking to expand, then Judo can be a great option.
It's also a matter of your opponents. If your division is full of the likes of Fedor, Akiyama, etc. then without a doubt you need to know how to stop their Judo. But so far is it uncommon, for the reasons I listed.
Ultimately the best choice is whatever good school you have available. For that reason you do not see Judo in MMA in the US, because Judo is not very high level in the US (unlike Japan or Russia).
Wrestling techniques aren't designed for MMA either, though being a gi-less sport definitely helps.
I think Judo is a perfectly good grappling style for MMA, though of course you'll have to adapt portions like you do with BJJ or wrestling. MMA grappling is much more related to clinch work and upright posture, because striking has to be taken into consideration. That lends itself very well to Judo, which is essentially a stand up clinch throwing art. Other than double and single legs, most of the TDs I see in MMA are very Judo-like, especially when pressed up against the cage. Inside and outside trips, footsweeps, you see these used all the time. Hip throws are rarer but far from non-existent. I think Judo's emphasis on top control and allergy to being on your back (in contrast to BJJ) helps make it effective as well.
Judo is hard to assess honestly, because unlike wrestling and BJJ we haven't really seen any young, elite Judoka at the top of their game make the transition to MMA. How many wrestling Olympic medalists have fought in the UFC, many shortly after winning their medals? How many BJJ world champs/medalists have made the transition when they were still in their prime? I bet you can name a few. Now ask the same question about Judoka: Ronda is the only one, and she's a bad gauge as female MMA is so underdeveloped relative to the men. The other Judo guys like Karo, Akiyama, and Hawn were never top level guys on the international scene (though they all were still able to put pretty much anyone on their back at will), but have still managed to have some success. I think this argument will be hard to settle until you start seeing people like Teddy Riner, Ilias Iliadis, and Ole Bischof switch to MMA when they still have a lot left to give athletically. Unfortunately, the countries that are really good at Judo are not generally big MMA countries (with the exception of Japan, but for some reason their elite Judoka rarely make the transition, and when they do it's when they're already too old to really climb the ladder), so it will probably be a while.
All that said, for someone just learning grappling for MMA I wouldn't make Judo my first choice only because so many techniques are gi specific. But I would definitely look at some Judo throws like ouchi gari, kosoto gari, footsweeps, uchi mata, osoto gari, and maybe kouchi gari because those are all great for throwing people from the clinch in an MMA context.