I was never really into Ultraman until I saw Tiga. I'll admit that it ws actually Tigas design that caught my eye. He just stood out to me more than the other Ultras, but I don't mean any disrespect to the Ultraheroes that came before him.
Tiga and Nexus are the Ultra shows I like for different reasons. To me Tiga is kind of like with Kamen Rider Black where you have a show that is sort of a middle ground between old-school and modern approach. I like his concept, the monsters, the mecha, and I thought the GUTS Team were all very likable. I think that if you've never really watched any Ultraman before Tiga is an excellent starter series.
Oh, and if you can find em on Amazon check out the manhua (Chinese comics) adaptation of Ultraman Tiga that Dark Horse brought over. The art is by Khoo Lung who's incredible work was also on Iron Marshall and SolarLord.