There is a reason why this is hailed as one of the anime greats. Because it is. I, perhaps, took much longer to watch this series than I should have done (honestly it took me three attempts to watch the whole thing through) and I can't say that I regret watching it. In fact, I regret not watching it earlier. Even though I will never say that I am a Mecha fan, I can safely say that Gurren Lagann is something special.
Even though it's nearly 10 years old (at the time of writing it's 10 year anniversary is only 4 days away) it stands the test of time. With a unique story and strong characters it is rocketed above many new anime and buries itself inside the hearts of many and I can totally understand why. As one of those series that people tend to recommend - it has to be something special and Gurren Lagann is something special. It's an experience from start to finish and definitely not one to pass up.
If you're looking for some good anime nostalgia, a good mecha series or just something different to watch - I could not highly enough recommend Tengen Toppa Gurren Lagann!