Gatland named his bumper 41-man squad for the 10-match tour on Wednesday, saying there was no clear stand-outs 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, long time," Hansen told reporters at Christchurch's Rugby Park on Thursday.
"There is depth all the way through, that's why people like [Dylan] Hartley and some of the Scottish boys have missed out because 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."
CLUTCHING AT STRAWS
Bookmakers, however, still expect the All Blacks to win 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 seized upon Ireland's shock 40-29 win over the All Blacks in Chicago in November as proof they were only human.
Hansen shot back that the Lions staff would not want to base their selections on that result, given the All Blacks defeated the Irish 21-9 two weeks later in Dublin.
"I’m pretty happy that our guys got some confidence beating Ireland in Ireland,” he told New Zealand's Radio Sport.
“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 middle of the pack and "grunty forwards" but said England captain Dylan Hartley, who was omitted, would have been an asset.
He rejected the idea that Gatland, who has stepped down as Wales coach to focus on the Lions tour, would unleash an expansive game in New Zealand.
"I'd expect we'll get a similar game-style to whatever we've got when we've played a Warren Gatland team," Hansen said.
"I think they'll tell us they will (be expansive), but I think they will want to win up front first."
(Reporting by Ian Ransom in Melbourne; Editing by Peter Rutherford)
