This question has been asked many times and also answered many times.
The reason there is no definitive answer probably is that the experience varies greatly from dreamer to dreamer and also between individual LDs.
So I will only speak for myself with this:
Generally, LDs are very real in the details but not anything like WL if I consider the whole experience. That is, individual sensations may be very real, but I can definitely tell I am in a dreamworld (only if I am lucid, of course
).
Maybe that is a good thing as well, after all, where would the fun be if everything was exactly as in WL? For example, I have no clue what it feels like to just take off and fly in WL, so the experience in a LD is as real as it can get. I just can say that it does feel very convincing. 
Realism varies greatly depending on the sense involved. In my LDs, visual details are always extremely realistic, for example if I look closely at some item, I wouldn’t be able to tell it from a real thing (except hands, of course
).
On the other hand, the scene as a whole often feels strange: It may have weird colors, be distorted, shaky or even dull in some way. I also tend to lose visuals if I son’t do anything for too long (quite annoying), but luckily I now seem to have found a way to get them back. 
Auditory senses are great. I can hear the dream world loud and clear, no matter what the source might be. Music often has an additional beauty to it in a LD that I have never experienced in WL.
Taste is mostly dull, like a shadow of what it should be in WL. It is somewhat “correct” in most cases (things taste like they should), but not very convincing overall.
Tactile sense is very good for me. Also, it is usually something that manages to keep me in the dreamworld. Everything feels quite real, even human skin. In fact, I really like to explore this in my LDs by touching everything. Actually, this is one thing that I used not pay a lot of attention to in WL. LDing has led me to explore how things feel in WL a lot more. 
As for smell… I never have paid much attention to it. Only in my last LD I actually got to spray around lots of Eau de Toilette, and it did smell somewhat real.
I shall put it on my todo list for upcoming LDs immediately. 
Also, there may be sudden “surges” in realism or intensity of the experience if you use certain techniques. This can change a dull low lucidity dream into an amazing LD in an instant.
There is also some truth in what Smiffy008 said, I think. If you (including your subconscious) do not pay attention to something in a LD or do not consider it important, it simply will not be there. If you really take a close look however, the experience can be amazingly realistic.
Anyway, good luck with your LDs! 