I agree that individually Lizarazu was the better player than Lahm. Lahm's tactical awareness is highly impressive though. He's such a smart player and he makes up for the flaws of the player in front of him, all the time, and helps to bring the best out of him. Ribery and Robben consistently played their best football with Lahm behind them. Since 2009 you basically just have to look at where Lahm played and you know instantly which player had more assists and goals. He's one of the reasons why Müller is scoring for fun this season as well, while he struggled for the first part of last season, when Lahm was playing on the left. Podolski is another example, he never looked out of place in the nationalteam until Lahm switched to the right. I think Lahm is underrated because he helps others to shine, different type of player and I don't mind if someone rates Maicon, Alves or Cole as better fullbacks during his time.
Individually Lahm is a way better right back than left back. Playing on the left for so long probably hurt his standing (which sounds crazy, because he became a world class player in that position). I wrote about it in one of the all time draft games:
Lizarazu was easily the better left back than Lahm. Lahm at his best playing as a right back is in my opinion on the same level, though.
Who do you think was a clearly better left back than Lizarazu during his peak? Of course, Maldini is the standout player in that position, but he's probably one of the best left backs of all time, so every full back of the last 25 years comes way short compared to him. Roberto Carlos was nowhere near as good as the hype around him suggests. I'd pick Lizarazu ahead of him. Can't think of another one.