I think it's telling to how great the game is if he didn't play 1-3 and still managed to give it a 9 out of 10 and loved it regardless.
Is it?
He's a newcomer, so everything's new to him, which may make things seem better than they are.
If he'd played the first 3, he might have scored this game lower because so much of the series is rinse-and-repeat. Still the same old combat, still the same old platforming.
What I found the most interesting about this video is that he calls out the game for not doing some things as well as the new Tomb Raider games, which to him was a minor issue, but to others might be more significant.
My issue with the series is that it seems to be content with mediocre gameplay mechanics, and when it does try something new, it either introduces mechanics that have been around in other games for years (the stealth in UC4 is much improved, but only because it FINALLY introduces basic stealth mechanics that actual stealth games have had for eons now), or it introduces some watered down mechanic of another franchise, like the pickax from TR.
At the end of the day, it's going to come down to what you value most in a game.
If great graphics, expertly directed cutscenes, and explosive setpieces are enough for you, then this game is great.
If you think that kind of thing is secondary to solid gameplay mechanics and pacing, then this game is average at best, and pretty bad at worst.
I'm not saying either way of looking at the game is the right or wrong one. I'm just saying it would be nice if people could accept that other people may value different things in games.