Mecha with Romance:
* Gurren Lagann: High-octane mecha action with a focus on teamwork, camaraderie, and romance amidst a struggle for freedom.
* Code Geass: Mecha battles with political intrigue and a strong focus on character relationships, including romance.
* Full Metal Panic!: Mecha action with a comedic touch and a central love story between the stoic protagonist and a bubbly school girl.
* Tengen Toppa Gurren Lagann: An even wilder and more action-packed version of Gurren Lagann with a focus on ambition and overcoming limitations.
Romantic Mecha with Magical Elements:
* Magical Girl Lyrical Nanoha: A series that starts with a magical girl premise but evolves into a high-powered mecha battle with strong romantic themes.
* Fate/Zero: A prequel to the popular *Fate/stay night* series that features magical battles with a focus on character relationships and complex narratives.
* Soul Eater: A series with a whimsical tone that combines the magical and mecha elements, featuring a dynamic cast of characters and a strong sense of camaraderie.
Anime with Similar Thematic Elements:
* Neon Genesis Evangelion: This classic series explores similar themes of human connection, existential dread, and the burden of responsibility, though it has a more psychological focus.
* Puella Magi Madoka Magica: This dark and philosophical series explores themes of sacrifice, friendship, and the true nature of magical powers.
* Serial Experiments Lain: A mind-bending series that deals with themes of identity, reality, and the impact of technology, though it's less action-oriented.
Ultimately, the best anime for you depends on what aspects of *Aquarion* you enjoyed the most. If you're looking for more mecha action, there are plenty of options. If you're interested in the romantic aspects, there are a number of series that focus on relationships and character development. And if you loved the magical elements, there are several anime that explore those themes in unique and fascinating ways.
I recommend checking out trailers and synopses of these shows to see which ones appeal to you the most. You may also want to consider exploring other anime from the same studio (Sunrise) as *Aquarion* to find similar styles and themes.