How much older is Gaara than Naruto? I presume it can't be by that much, certainly not between 25-30 (I would say younger, maybe 18-19 at most)...I think what's happening here is that there's this tendency to use our real world logic and socially acceptable behavior, and apply it to a universe of ninja fantasy. I say separate the two. If one is gonna be critical, do it from the standards of that universe, not ours. That is not to say that one should not use logic, on the contrary. Use it, but within the proper context.
I will start out with the belief that there's more to being Hokage than knowing tons of jutsu's. For example, the talent of charismata. From early on, Kakashi and others have stated that Naruto has this unspoken ability to motivate others through his inspiration and/or will (remember the Great Naruto bridge?). If that wasn't convincing enough then what about the "hearts" Naruto has changed thru TNJ? It is not a coincidence. In more recent evidence, Gaara made the motivational speech that kept the Ninja alliance from falling apart. Also, charisma was exemplified when the 5 Kages finally showed up to the main battlefield and rejuvenated the Ninja Alliance's morale by just their presence and leadership. Naruto has displayed this component of being Hokage by the charisma he brings, similarly to how the other Hokages have been shown to have as well. They were all able to accomplish this in the Naruto universe because its people recognize something, a trait, a characteristic, a strength, worth following, and thus where chosen to lead.
Which brings me to my other major point: Recognition. Starting from the First, he literally created the current Ninja village system (with Madara's help ofc). The Fifth created the incorporation of medical ninjas in squads. The Third was know as the "professor." Naurto's dad was known for his genius intellect, and specially his incredible speed; similar to the Second. If it wasn't for Tsunade--a legendary Sanin--Kakashi, because of his famous Copy Cat sharingan, would of been Hokage. All the Hokages were accomplished people, despite of their personal flaws. As for Naruto, a jiinjikuri, practically solo'd Pain, thus saving his village from total destruction. And in case it escaped noticed Naruto became his village's Hero since then; they finally recognize his worth. And now, with this war, the whole Ninja world knows who Naruto is, who's currently in the front lines fighting in par with the likes of Leaf's former Hokages, partnering up with Kurama (an unheard feat beforehand), and holding his ground against the actual Madara, a legend by its own right. In short, Naruto is upfront and center, and everyone knows it.
Now, in our real world there are many arguable traits that makes a great leader. Among many of them, to name a few, are: visionary; courage; intelligence (battlefield and otherwise); inspiration & motivation; Strength (in all its different forms); Will; and honor. Lets apply these characteristics to the Hokage traits in the Narutoverse, and I ask you: do you see a connection? (doesn't mean you have to agree, but at least see the connection). If not, I rest my case because then I have failed to communicate effectively my perspective on Naruto. But if so, then think about its significance for the kids who are reading this Manga. Think about it.
If I'm not mistaken, your criticism of Naruto being too young to lead is from his lack of real world understanding. In other words, he lacks wisdom and maturity. I disagree with that. For starters Naruto understand how to connect with people better than most, which is due from his lonely and ostracized upbringing and the pain from those experiences serves greatly for compassion for others (another quality in leadership). He also traveled and was taught by none other than Jairaya, a womanizing legendary Sanin. Need I say more on that. The latest, however, is his development in his overcoming of his own insecurities, hatred, and other people's nature.
I could go on. But I'll leave it at this.
I know its long. I just hope you at least see things a little differently. Great leaders are wise enough to know when to be firm and when to compromise; to understand without arrogance, and conquer through submission. So, enough about jutsu's. Narrow focus on that alone is being legalistic. The bigger picture are the qualities of being Hokage, a leader, and whether Naruto fits them. I say yes, he will become Hokage.
