Gatland named his bumper 41-man squad for the 10-match tour on Wednesday, saying there was no clear standouts for starting players in a number of positions.
World Cup-winning coach Hansen was impressed by the depth at Gatland's disposal for the tour, which includes three Tests against the All Blacks.
"I think this is the best British and Irish Lions that we've seen come here for a long time," he said. "There is depth all the way through. That's why people like Dylan Hartley and some of the Scottish boys have missed out - there's so much depth.
"It's going to be a very good side and they'll come with a lot of expectation, which I think is going to be interesting to see how they cope with that. A lot more expectation than they've been used to because people expect them to win."
Bookmakers, however, see the All Blacks taking the series 12 years after they whitewashed a Clive Woodward- led Lions squad laden with English World Cup winners.
With five matches against New Zealand's dominant Super Rugby teams, Gatland said the Lions faced the "toughest tour," but pointed to Ireland's shock 40-29 win over the All Blacks in Chicago in November as proof they are only human.
Hansen shot back that the Lions staff would not want to base selections on that result, given the All Blacks defeated the Irish 21-9 two weeks later in Dublin.
"I'm pretty happy our guys got some confidence beating Ireland in Ireland," he said, but "you're clutching at straws if that's how you are selecting teams. You pick players who can do the job you want them to do and play the style of game you want to play."
Hansen said there were no major surprises in Gatland's squad with its "big ball carriers" in the middle of the pack and "grunty forwards." But he said England captain Hartley, who was omitted, would have been an asset.
He rejected the idea that Gatland, who stepped down as Wales coach to focus on the Lions tour, would unleash an expansive game. Rather, Hansen expects a similar style to what he has been seen with other Gatland teams. They could say they will be expansive, he said, "but they will want to win up front first."