Don't bother with original Mount and Blade. Play Warband instead. Warband is plain and simple better MnB in every aspect.
There is no reason to play first one instead of Warband, unless you just need to try every single one. But there really is no reason to try it.

Then, if you enjoy Warband (and I don't see why one wouldn't) get Viking Conquest and perhaps Fire & Sword too.

Well, for my 2p worth: Goto warband, its most improvements over the first. Not to mention most mods are for warband. I would recommend, when you have practiced for a bit on vanilla warband: Floris modpack, then prophesy of pendor or brytenwalda (depending on if you like low fantasy or Vikings). POP is the best mod out there, but it is brutally hard at points. As for the official addons, played Viking recently, didn't get on with it at all. Brytenwalda is very similar to Vikings, but just feels better overall.
Do be prepared to spend some time, great game though.

Play the Warband. It is actually same game with everything better.

i believe I've read Sach say that the Fire&sword was worse than a player made mod that was available.

I know ragnar has a ton of hours on warband and has mods, either of those guys can probably tell you some good insight....

Where is that ape anyway?

I actually like the original much more than Warband. Warband I start up and begin to play but it never holds me for very long. Whereas I can play the original for hours upon hours and never really bore of it.

I also like With Fire and Sword a lot. Once again Warband just isn't that interesting to me. SO I would recommend getting all three, play the original for a while, see how you like it then play either Warband or With Fire and Sword and see if you like them better. If you do you will not benefit too much from the original anymore I shouldn't think but you'll have a good idea for how the mechanics work and can most likely appreciate the work that went into creating the series if nothing else.

Just tired the original and mount & blade.

I decided to stay at mount & blade because it give more options for control.
I am having trouble attacking enemies on horse in the original mount & blade because of the control.

For vanilla gameplay, Get Mount & Blade: Warband. It's got much stronger gameplay overall than the original, and a ton of great complete overhaul mods.

However I'd also suggest picking up the original Mount & Blade (on sale) so that you can play a mod named1866, a complete overhaul that might just be the best old west game available for PC.

I've got no opinion on any of the DLCs as I don't own any of them.
Sorry, didn't see that you just posted this. So you're gonna stick with the original? Don't forget to grab 1866! Also, there is a demo of Warband available on Taleworld's official site, if you want to give it a try.

Nope, I plan to stick with the more advance warband because I have some trouble attacking on horse in the original.

here. and yes, fire&sword was gash!

Warband is an expanded version of the original, so you can probably just skip the original. Fire and Sword did not get a great reception but I have not played it myself so will not comment on playing it.

I own all of them...

I'd get Warband and then Viking Conquest since you need Warband to play it. Viking Conquest is hands down the best version with the most features. Yes it was buggy as shit in the beginning but the devs released constant patches and it is far far more stable today. If you want a lot of features and a challenge then VK is really what you want.

Wasn't Viking Conquest made by the Prophesy of Pendor mod team? Or the Brytenwalda mod team?

Yes, by the brytenwalda team.
What's great about it then? I found controls seem to be broken (latest version) in that swining a weapon just stopped half the time. Then it was too much of a grind to start, you literally have to spend days in the arena to get a shield - which is no1 necessity in an age of melee. That's not fun, but you cant even attack a bandit even if you hire several men. Personally I found brytenwalda easier to get into, maybe as trading seemed to give plenty of money.
Also, is there not something about things from brytenwalda not being in vc as ip of other people?
Person all I always end up going back to POP.

I haven’t played them yet, but I read somewhere that the original has a much greater mod library due to it being older?