The only thing I think is a bit disappointing, is that the majority of quests leans toward a certain faction.

I can be seen that way. NCR was the first major faction in the area. So they are set up pretty well. I find asking questions I can get quests that go against NCR. Trick is not getting NCR mad at you to early they can make things hell for you, since they are everywhere. I have been able to get really good rep with both NCR and the Legion.

some what off topic sorry.

It just seems that way, I'm not saying that it is... still going through my first play of FNV and seemingly NCR is a larger faction imo.

But indeed, I'm trying to do the same as well: to get the most quests from different factions without upsetting either one of them. I succeeded in that but for how long is another question and till now I only have a problem with the powder gang as a result of wanting to help the inhabitants of Goodsprings early on in the game because they helped me (Karma, karma!), although I got a bit of fame back by releasing certain powder gang hostages from the claws of the legion undetected. Also had to ditch Boone for a while because he wanted to massacre the legion which I found understandable regarding his background, but not welcome for my strategy at the time.

The more I progress in the game, the more I believe that eventually I have to pick a side. It doesn't matter, however. That's why I'm trying to trigger most of the quests to see which side/faction suits me best and to indulge myself in as much possible story/quest lines there are.

On my next replay I promised myself to do the exact opposite: being an egotistical, narcissistic, not helping anybody but me evil person; to see how this plays out in NV.

It shouldnt be hard
Unlike F3 in this game you have whole faction with you if you are evil
Legion