>ecchi
Haganai
Bakemonogatari (it's more of a supernatural mystery show rather than a romance-based one, but it still has a harem of girls)
To Love-Ru (first season is legitimately good, everything after that slowly becomes softcore porn)
Oniichan no Koto nanka Zenzen Suki ja Nai n da kara ne!! (quite literally the only anime I've ever thought was pretty funny throughout)
>not ecchi
The World God Only Knows
Isekai no Seikishi Monogatari (it's a spin-off, but you don't need to watch Tenchi Muyo to enjoy this, it's strong enough to stand on its own) (also it's more of an action-adventure show but it's still a male lead with a supporting cast of females)
Nisekoi