Battle for Middle-earth I and II were two excellent Lord of the Rings games into the era of HD graphics.
The HD mods are essentially texture packs, featuring both reworked and all-new unit and hero models. Battle for Middle-earth 1: HD Edition and Battle for Middle Earth 2: HD Edition were both released in 2017, and both are still getting ed in 2021 as the mod team works on version 8.0. BFME2 even has a version to the also popular Age of the Ring mod.
Original publishers EA were forced to switch off the official servers on New Year's Eve 2010 due to the expiration of their Lord of the Rings videogame licence, but you can still play multiplayer games of BFME 1, 2, and Rise of the Witch-King via the T3A: Online unofficial server and through services like GameRanger.
Best of all, the HD edition mods are intercompatible, meaning you can use them online even if your opponent doesn't have them installed.
Something else that's also worth paying attention to is the Battle for Middle-earth: Reforged project, also known as BFME: Reforged. Like all mods, this is highly unofficial, but its aim is to completely rebuild Battle for Middle-earth in Unreal Engine 4 with modern graphics. The mod has been in development for a few years now, but we got our first glimpse of gameplay in 2020:
The team's most recent update was posted in April 2021 and looks at the changes coming to the Elves, as well as other bits of progress. There's no release window for when this will be finished, but fans seem excited. We're concerned that this mod strays beyond the realm of simply modding what's already there, so keep that in mind.
In the meantime, you can grab Battle for Middle-earth: HD edition here, and Battle for Middle-earth II: HD edition here. Installation is easy, although it's worth a reminder that the original games aren't available to purchase any more, digitally or otherwise, so you'll have to dig out your old discs or find one second hand.
Maybe if we wish hard enough we can get a Battle for Middle-earth 3?