Compared to a motor car, or a tablet computer, flashlights are relatively simple in their engineering and manufacture, hence a company does not have to be big like Toyota Motor Corporation or Samsung Electronics, to engineer flashlights.
Thus, there are many flashlight brands.
And many of them are good.
Each in their own different ways.
A flashlight that is good for one person, may not be good for another person.
So, it's horses for courses too.
Good brands include:
4Sevens.
Sunwayman and their V10R, V20C, T20CS 1x18650 with 278 meters of throw, T40CS, and V60C.
Zebralight and their SC600 [my current EDC]; btw, I think Zebralight is good, but it's not God - up to you who you want to believe.
Jetbeam with some popular RRT-0 pocket and the old RRT-3 1200 lumen thrower.
Nitecore have a lovely Tiny Munster - one of the top big multi-18650 floody flashlights.
HDS with their 1xCR123 size flashlights.
omglumens makes some lovely Deft EDC LR throwers.
Eagletac and their new G25C2, and the M3C4 XM-L too.
Surefire and their lovely Total Internal Reflection TIR hybrid reflector-lens like the Invictus UB3T etc.
LedLenser is peculiar, but make some lovely lights with zoomable lenses too.
Armytek makes some lovely throwers.
Fenix is good too with some lovely models.
Thrunite make some lovely lights too eg Catapult, and TN11 etc.
Olight and their 6x18650 SR90 with 634 meters of throw, or the SR92 6x1860 Triple XM-L flooder with 425 meters of flood-throw.
New kid Crelant has a superb 7G5 thrower, while Xtar has a class leading 470 meter flood-thrower.
That's 15 brands already?
Etc etc, many more...
Thus, I don't think it is pertinent to rate the top 5.
I think rating the 5 best selling brands could also be misleading too; the best selling, is not necessarily the best product.
Worse, what's good for one person, may not be so good for another person.
Rather, look at your own personal needs and wants, and treat each flashlight model on its own merits, as it tries to fulfill your needs and wants.
It's not like the world of cars, where Ferrari, Porsche, Mercedes and BMW etc, are always at the top.
Cars have relatively less competition, because you need big money, and we need to collaborate a lot of different types of engineers together, in order to produce a motor car.
Another example - with tablet computers, there is the top 3.
It is the Asus Tranformer Prime for the best hardware with a 1.3 GHz quad core and keyboard dock with 18 hours battery life, or the Samsung Galaxy Tab 10.1 for the most vibrant organic AMOLED oLED colours and highest contrast screen, or the Apple iPad2 with the largest choice of software - something which the other manufacturers who so far focus on the hardware, have yet to master.
You godda be a big multinational to produce a tablet computer.
However, it is not so cut and dry with flashlights - with many more top brands available.
Flashlights are like clothing.
Clothing is also simple to engineer and fabricate.
Thus, there is also a plethora of brands of clothing available.
Talking about the Top 5 flashlight brands can be rather misleading, and more often than not, very controversial and disputable as to who should be included or not ...