I feel really old reading this thread. Seriously when I started martial arts about 12 years ago everyone knew that some arts were grappling arts and some were striking arts. Boxing, Muay Thai, TKD, Kickboxing and Karate were the striking arts and Judo, Wrestling, Aikido and Jujutsu were the grappling arts. Everyone knew this.
Then the UFC and BJJ came along and now all you kids with your new fangled ideas think that the only grappling art is BJJ. I feel so old.
Of course not...however, BJJ offers us the best chance these days of experiencing grappling with the most minimal amount of rules and the use of a Gi/clothing with maybe the exception of sambo.
There is the GAME of BJJ which is played alot on your back and in many respects does not represent reality per se.
BUT, from all my experiences, I have found it to be free enough to be a wonderful fit to work through the same lessons we are dealing with in aikido.
Judo is also a wonderful art and does a great job of working throws, however, it has become such a sport that has become almost too and they simply do not practice ne waza enough in most cases to make it a good match for learning the lessons we are trying to learn in aikido.
That said, Judo is also a decent fit I think out of all the grappling forms since it does have the basic elements and you have a Gi/Clothing.
Sambo, which is not as well known in the US is very good as well...and they wear a Gi.
Then there are all the forms of wrestling which do not wear a Gi. I prefer Greco Roman as an Adjunct practice because of the rules dealing with throws and takedowns which allow someone to learn some very good skills in this area without a gi.
But again, it does not have a Gi so very difficult to work on developing skills and slowing down the fight to a workable level. I find that speed, agility, and athleticism become very important factors since you don't have a GI.
Done right though, it can be a very good practice as well...I just think wrestling with No Gi's are harder to learn and do not approximate "DA STREET" maybe as well as GI based arts.
Submission Grappling (NO GI) is decent, but you will find that most guys that do this sport spend a fair amount of time in a GI as well to round out there training.
I know several coaches in the UFC area that are advocates of there guys training with Gis in order to develop skills.
That, however, is a constant debate in the GI/NO GI community about which is better for MMA type fighting.
Anyway, as usual YMMV. I simply prefer BJJ as I have found it to be technical enough, and slow enough to allow you the opportunity to fully explore the principles we are trying to explore.