are any worth checking out?

All

League of Legends
I've played Tiberium Alliances but it soon became boring for me.
And that's about all I've paid attention to :P

There are some I've tried out and were pretty amazing. But they tend to get boring after a while. So not all are worth checking out IMO

Just got LoL. Looks good, but only played one game so far :P

Are you looking for online games to check out in general? Or just specifically curious about the ads?

Tried that WWI strategy game, but you have to check pretty regularly and a single game takes anywhere from 20-100 days apparently (though you can join as many as you like).

I'm level 29 in LoL, couple more games to the maximum level of 30... I suggest playing with friends if they play since playing with random people may not give you the best experience ;)