I think that "perfect" does not exist. Besides, even if one laptop were perfect today, it might not be in a few months or in one year. Besides, it can only be perfect depending on what you plan to do. Different needs require different machines.
When I buy an expensive laptop my number 1 concern is that it runs into problems. Even under warranty, it is annoying to send them back and forth. So, I read a lot to find out which brand has the best customer service. And, lately I started to favor using a re-seller, in particular if there is one near me because it means that I can take the computer to them in case I wanted to upgrade it or, I hope not, needed to have it fixed. While I like the Alienware brand, this seems to be their weak suit. Many will tell you that since they are owned by Dell, they have become Dell-ware instead of the original Alienware. It is true? I do not know, but just the idea to have a $4000 machine running into issues scares me to death.
Do not just go for the flashy. True, the HP Omen in my opinion has a super ugly logo, HP should be kicked in the head for having an absurd logo like that, but it feels solid. Also their specs do not even reach the level of MSI, Asus, Alienware, etc. But, if you don't need a super laptop, you can have a good one for considerable less money. Also, I think that HP's are quite reliable. Sure you find complaints, but compare the number of complaints to the number of items sold. How many people buy a high-end Alienware vs. an HP Omen? So maybe 100 complaints for the Omen are %-wise less severe than 10-20 complaints on an Alienware.
Be very careful about the specifics you want. For instance, If it had been available i would have bought an Asus G800VI. Period. It was supposed to cost ~$4500+ some extra = $5000. It is a lot, I know, but I truly loved the looks and the huge size. I could have gone with the Asus G701VI which is not equally beautiful, but close enough. Why not, then? Well, these machines only come in RAID configuration (RAID 0 or RAID 1). Now, I use it for work and while RAID 0 is fast and good for gaming, it is enough that one of the two SSD's runs into any trouble and then I lose everything. I can reinstall a game or two, more complex reinstalling professional and scientifc software which also requires time. RAID 1 is very safe. It is not a backup because if the computer burns, say, you lose everything the same. But it is a waste as I can do it much cheaper with an external hard drive. So, even if it pains my heart I decided against these beautiful machines. Besides Asus pissed me off by announcing them and then pulling them from sales. It makes me wonder if they are running into issues with heat dissipation when using the GTX 1080.
Be very wise choosing between 4K and FHD screens. If you are a gamer, 4K might be the right choice, but then make sure that you have a very strong CPU and GPU. Probably only SLI can really allow you to play games in 4K with satisfactory frame rate. However, again, if you plan to use your laptop also for work, be warned that a lot of important softwares do not scale well at all on 4K screens and you will be swearing like a sailor every day you need to use your computer for work or for school projects. This is not the computers' fault. It is the silly software makers who pretend that 4K is not important. In a few years we will be all 4K, but it is still a few years away. Plus, they are already talking about 8K...
It is not true that i7 6820hk is the top.. You can have the i7 6920hq as well. Look at the top MSI GT83Titan VR with 2 SLI GTX 1080 (I think it runs for around $4500-5000). But, before you worry about "hq" or "hk" and overclocking.. make sure that your machine allows you to overclock your CPU with ease since on some machines it requires some knowledge and that it is well built to dissipate the extra heat that this process generates.
Also look at how sturdy the construction is. Sadly, more and more plastic everywhere.. Should be all carbon fiber and aluminium. A beautiful warped screen is not that beautiful anymore. In this sense, Alienware bodies are still very good, better than MSI and Asus in my opinion.
Look for customizations. If you want to upgrade your machine, can you do it? Alienware for instance limits the run to 32GB, while MSI and Asus allows for 64GB, HP I think get only to 16GB. 16GB fine today, but in 1 year? How many SSD slots, is it easy to open, etc...
If you find size important, check the weights. Razer is about to come out with the thinnest 17.3" laptop sporting a GTX 1080. It will cost quite a bit, but how is the heat dissipation. You might be the guinea pig when you buy a very new model. That is something to keep in mind too as you want something you can use and that is reliable. Usually the thinner the laptop, the more likely it is to have heat issues.
Check the noise level. If you have the coolest computer in town but that laptop blows like a train, you are not going to impress anyone and if you are at a library, you could even upset some people.
I hope you got my jest. There is no such thing as "perfect". You need to pick what is right for you.
Cheers.